Photovoltaic Energy Generation Device

ABSTRACT

Photovoltaic energy generation device comprising several cells ( 11; 111 ), comprising a photovoltaic cell ( 7 ), comprising one or more elementary photovoltaic cell(s), and a storage element ( 8 ) connected to the terminals of the photovoltaic cell, characterized in that it comprises several subsets of cells ( 11; 111 ) and switches ( 103, 104 ; K 7 , K 8 , K 9 ) disposed between these subsets able to dispose two subsets in series or in parallel.

The invention relates to a photovoltaic energy generation device. Italso relates to a method for managing the generation of photovoltaicenergy.

The generation of photovoltaic energy is generally implemented by anenergy generation device comprising the association of a multitude ofelementary photovoltaic cells, possessing a low voltage across theirterminals, disposed in series so as to attain a desired output voltage.Often, this photovoltaic energy generation device is connected to theelectrical distribution network, which requires a voltage of a fewhundred volts from it. In practice, a disparity is noted in thesituations and behaviours of the various elementary photovoltaic cellsof the generation device since some of these cells may have failed,others be in a shaded zone, etc. It follows from this that an energygeneration device is not optimized since its photovoltaic cells do notoperate at their optimal operating point.

FIG. 1 illustrates by way of example a photovoltaic energy generationdevice 1 linked to the mains 5, by an intermediate device 6 of DC/ACconverter type. The function of the device 6 is to transform the outputvoltage of the photovoltaic generator into an alternating voltagecompatible with the mains 5. Naturally, the use of this intermediatedevice 6 exhibits several drawbacks, including the generation of lossesat the level of the transistors and other components used, therebygiving rise to additional energy consumption globally. Moreover, thisalso represents additional bulk.

Document U.S. Pat. No. 4,175,249 describes an energy generation devicewhose structure comprises a multitude of switches, to make it possibleto dispose certain photovoltaic cells in series or in parallel, so as toafford flexibility in electrical generation. However, this solutionremains non-optimized and difficult to manage in practice.

Thus, there exists a need for an improved solution for photovoltaicenergy generation making it possible to resolve the drawbacks of theexisting solutions, and the invention seeks to attain all or some of thefollowing objects:

A first object of the invention is to propose an optimized solution forphotovoltaic energy generation.

A second object of the invention is to propose a photovoltaic energygeneration solution which allows flexible generation, adapting tovarious requirements of use, such as to the variable needs of a motorfor example or of an arbitrary electrical network.

For this purpose, the invention relies on a photovoltaic energygeneration device comprising several cells, comprising a photovoltaiccell, comprising one or more elementary photovoltaic cell(s), and astorage element connected to the terminals of the photovoltaic cell,characterized in that it comprises several subsets of cells and switchesdisposed between these subsets able to dispose two subsets in series orin parallel.

The photovoltaic energy generation device can comprise at least one cellassociated with at least one cell switch, so as to be able to disconnectit from the remainder of the photovoltaic energy generation device.

The photovoltaic energy generation device can comprise several modulesdisposed in series comprising at least one cell, and each subset ofcells can comprise one or more modules linked in series.

Each module can comprise a lower terminal adapted for connection with alower module and an upper terminal adapted for connection with an uppermodule, and the device can comprise a module comprising at least onebranch between its lower terminal and its upper terminal comprising acell and a cell switch disposed in series.

The photovoltaic energy generation device can comprise switches forinverting the voltage across the terminals of all or part of thephotovoltaic energy generation device and/or modifying the assemblage inseries or in parallel of subsets of the photovoltaic energy generationdevice, which are controlled by at least one control circuit disposed atthe level of a module or of a subset of the photovoltaic energygeneration device.

The photovoltaic energy generation device can comprise at least oneprocessing circuit at the level of a module or of a subset and/or acentral computer, which drives(drive) cell switches or module switchesor parallel switches and/or switches disposed between subsets so as tomodify the assemblage in series or in parallel of these subsets and/orswitches to invert the voltage across the terminals of all or part ofthe photovoltaic energy generation device, by way of a control circuit.

The photovoltaic energy generation device can comprise a processingcircuit at the level of a module and/or a central computer whichimplements regulation of a value of voltage and/or output current of thephotovoltaic energy generation device around a setpoint value bycomputing the number of subsets to be disposed in series or in paralleland by actuating the switches disposed between these subsets.

The photovoltaic energy generation device can comprise several modulesdisposed in series each comprising several cells disposed in paralleland/or series, each cell being associated with at least one cell switchand each cell comprising a photovoltaic cell, comprising one or moreelementary photovoltaic cell(s), and a storage element connected to theterminals of the photovoltaic cell.

The photovoltaic energy generation device can comprise an arrangement ofbricks comprising two parallel branches comprising respectively a celland at least one cell switch and at least one cell switch and a cell,and comprising a transverse branch linking the two intermediateterminals of respectively the said two parallel branches, thistransverse branch comprising a cell switch.

The photovoltaic energy generation device can comprise at least oneH-bridge able to invert the voltage across the terminals of all or partof the photovoltaic energy generation device.

The photovoltaic energy generation device can comprise at least onemodule switch connected in parallel with a module or at least onemodule, each cell of which is associated with a parallel switchconnected in parallel with the said cell and a cell switch disposed inseries, and/or at least one switch disposed in parallel with severalmodules.

The photovoltaic energy generation device can comprise a sensor formeasuring the current at the level of a cell, and/or a sensor formeasuring the voltage across the terminals of a cell and/or across theterminals of a cell switch, and/or a sensor for measuring thetemperature of a cell and/or for impedance spectrometry measurement.

The cell switch and/or module switch and/or parallel switch can be atransistor and/or the storage element can comprise at least onecapacitor.

The photovoltaic energy generation device can comprise three columnseach comprising several modules disposed in series to provide athree-phase output.

The invention also pertains to a method for managing a photovoltaicenergy generation device such as previously described, characterized inthat it comprises a step of computing the number of subsets of thephotovoltaic energy generation device to be disposed in parallel or inseries and a step of determining the position of switches disposedbetween the subsets so as to attain the computed number.

The method for managing a photovoltaic energy generation device cancomprise a step of determining the position of several cell switchesand/or of several parallel switches of several cells disposed inparallel so as to maintain cells of the photovoltaic energy generationdevice in an operating state in a range around an optimal operatingpoint.

The method for managing a photovoltaic energy generation device cancomprise the following steps:

-   -   a first computation of the ratio between the desired output        voltage of the photovoltaic energy generation device and the        mean voltage of a subset, thereby giving the number N of subsets        to be placed in series so as to attain, under no load, the        desired output voltage;    -   computation of a mean deviation between the voltage of the        subsets and their optimal voltage, and feedback so as to        approach the optimal situation, by modifying the output current        so as to approach a more favourable situation to attain optimal        operation at the level of each subset;    -   selection of the N particular subsets to be used, by taking        account of the deviation between their voltage and their optimal        voltage.

The method for managing a photovoltaic energy generation device cancomprise a step of regulating the voltage and/or the output current ofthe photovoltaic energy generation device so as to follow a setpointvalue.

The setpoint value can be variable over time, be for example sinusoidal.

The method for managing a photovoltaic energy generation device cancomprise a step of increasing the number of subsets in series if theoutput voltage of the photovoltaic energy generation device is less thanthe setpoint value and a step of decreasing the number of subsets inseries if the output voltage is greater than the setpoint value.

The method for managing a photovoltaic energy generation device cancomprise a step of limiting the frequency of variation of theconfiguration of the photovoltaic energy generation device so as toattain regulation with regard to a mean value while preventing thenumber of subsets in series from exhibiting too much oscillation.

The method for managing a photovoltaic energy generation device cancomprise the following steps:

-   -   when the voltage across the terminals of a cell exceeds an        optimal voltage corresponding to the optimal operating point,        increased by a predefined percentage, at least one cell switch        is closed so as to allow its use to produce a voltage and a        current towards the output of the device, and/or    -   when the voltage across the terminals of a cell falls under this        optimal voltage decreased by a predefined percentage, at least        one cell switch is opened, so that it no longer participates in        the production of voltage and current at the output of the        device.

The method for managing a photovoltaic energy generation device cancomprise a step of charging of a storage element by a photovoltaic cellduring its disconnection from the remainder of the device.

The method of management of photovoltaic energy generation device canimplement the following steps:

-   -   mutual balancing of the modules and/or cells and/or subsets,        using by priority the modules and/or cells and/or subsets whose        voltage is the highest; and/or    -   balancing of the modules and/or cells and/or subsets by        modifying the mean rate of use of the modules and/or cells,        and/or subsets but without using the same modules and/or cells        and/or subsets permanently, so that the voltage of the modules        and/or cells and/or subsets balances.

The method for managing a photovoltaic energy generation device cancomprise a step of supplying electrical power to a control circuit for acell switch and/or switches disposed between subsets able to dispose twosubsets in series or in parallel and/or for a parallel switch on thebasis of at least one cell of the photovoltaic energy generation device.

The invention also pertains to a photovoltaic energy generation devicecomprising several modules, characterized in that a module comprises atleast one cell and at least one cell switch associated with the cell, soas to be able to disconnect it from the remainder of the photovoltaicenergy generation device, this cell comprising a photovoltaic cell,comprising one or more elementary photovoltaic cell(s), and a storageelement connected across the terminals of the photovoltaic cell.

Each module can comprise a lower terminal suitable for connection with alower module and an upper terminal suitable for connection with an uppermodule, and can comprise a module comprising at least one branch betweenits lower terminal and its upper terminal comprising a cell and a cellswitch disposed in series.

The photovoltaic energy generation device can comprise an arrangement ofbricks comprising two parallel vertical branches comprising respectivelya cell and at least one cell switch, and at least one cell switch and acell, and comprising a transverse branch linking the two intermediateterminals of the two vertical branches and comprising a cell switch.

The photovoltaic energy generation device can comprise at least onesensor for measuring a quantity characteristic of the state of a cell,and comprise, at the level of a module, a control circuit for at leastone cell switch to control it as a function of the quantitycharacteristic of the state of the cell.

The photovoltaic energy generation device can comprise a control circuitfor at least one cell switch directly supplied electrically by at leastone cell of a module of the photovoltaic energy generation device.

The control circuit for at least one cell switch can be powered by atleast one cell in proximity to the cell switch that it drives.

The photovoltaic energy generation device can comprise several modulesdisposed in series each comprising several cells disposed in paralleland/or series, each cell being associated with at least one cell switchand each cell comprising a photovoltaic cell, comprising one or moreelementary photovoltaic cell(s), and a storage element connected acrossthe terminals of the photovoltaic cell.

The photovoltaic energy generation device can comprise several cellseach associated with at least one cell switch, controlled by one or morecontrol circuit(s) supplied electrically directly by at least one cellof a module of the photovoltaic energy generation device.

The photovoltaic energy generation device can comprise a sensor formeasuring the current at the level of a cell, and/or a sensor formeasuring the voltage across the terminals of a cell and/or across theterminals of a cell switch, and/or a sensor for measuring thetemperature of a cell and/or for impedance spectrometry measurement.

The photovoltaic energy generation device can comprise at least onemodule switch connected in parallel with a module or at least one moduleeach cell of which is associated with a parallel switch connected inparallel with the cell and a cell switch disposed in series, and/or atleast one switch disposed in parallel with several modules.

The photovoltaic energy generation device can comprise at least oneprocessing circuit at the level of a module and/or a central computer,which drives(drive) cell switches or module switches by way of a controlcircuit.

The photovoltaic energy generation device can comprise a centralcomputer and a communication bus linking the various modules comprisingat least one cell switch to the central computer by way of a galvanicisolation.

The photovoltaic energy generation device can comprise an electroniccard comprising:

-   -   terminals for a link with cells of the photovoltaic energy        generation device, and    -   cell switches for one or more modules, and    -   sensors for measuring a quantity characteristic of the state of        cells and/or a control circuit for the cell switches.

The photovoltaic energy generation device can comprise at least oneH-bridge able to invert the voltage across the terminals of all or someof the photovoltaic energy generation device.

The photovoltaic energy generation device can comprise several subsetsof cells and switches disposed between these subsets able to dispose twosubsets in series or in parallel.

The photovoltaic energy generation device can comprise switches toinvert the voltage across the terminals of all or some of thephotovoltaic energy generation device and/or modify the assemblage inseries or in parallel of subsets of the photovoltaic energy generationdevice, and these switches can be controlled by at least one controlcircuit disposed at the level of a module of the photovoltaic energygeneration device.

The cell switch and/or module switch can be a transistor.

The storage element can comprise at least one capacitor.

The photovoltaic energy generation device can comprise three columnseach comprising several modules disposed in series so as to provide athree-phase output.

The invention also pertains to a method for managing a photovoltaicenergy generation device which comprises a step of determining theposition of at least one cell switch so as to maintain the photovoltaiccell in an operating state in a range around an optimal operating point.

The position of at least one cell switch can maintain the cell in anoperating state in a range of plus or minus 5% around an optimaloperating point.

The method for managing a photovoltaic energy generation device cancomprise the following steps:

-   -   when the voltage across the terminals of a cell exceeds an        optimal voltage corresponding to the optimal operating point,        increased by a predefined percentage, at least one cell switch        is closed so as to allow its use to produce a voltage and a        current towards the output of the device, and/or    -   when the voltage across the terminals of a cell falls below this        optimal voltage decreased by a predefined percentage, at least        one cell switch is opened, so that said cell no longer        participates in the production of voltage and current at the        output of the device.

The method for managing a photovoltaic energy generation device cancomprise a step of charging of a storage element by a photovoltaic cellduring its disconnection from the remainder of the device.

The method for managing a photovoltaic energy generation device cancomprise a step of comparing the actual state of a cell with an optimaloperating state, stored previously in an electronic memory, or a step ofsearching for the optimal operating conditions of the cell.

The method for managing a photovoltaic energy generation device cancomprise the implementation of the following steps:

-   -   measurement of a quantity representative of the state of a cell        and transmission of the measured quantity to at least one        computer;    -   determination of the position of a cell switch and/or module        switch by taking into account the measured quantity;    -   transmission of a command for opening or closing a cell switch        and/or module switch as a function of the preceding        determination.

The method for managing a photovoltaic energy generation device cancomprise a step consisting in diagnosing a failure and/or an at-riskstate of a cell, by recognizing defective cells, such as overheatingsubsequent to a situation of short-circuit, ingress of moisture,electrical arcing, flame, isolation defect, on the basis of the quantitymeasured at the level of a cell, so as to disconnect or discard from theoverall operation of the photovoltaic energy generation device the cellconcerned, by opening its cell switch and/or by closing the moduleswitch concerned.

The photovoltaic energy generation device management method canimplement the following steps:

-   -   mutual balancing of the modules and/or cells, using by priority        the modules and/or cells whose voltage is the highest; and/or    -   balancing of the modules and/or cells by modifying the mean rate        of use of the modules and/or cells, but without using the same        modules and/or cells permanently, so that the voltage of the        modules and/or cells balances.

The method for managing a photovoltaic energy generation device cancomprise a step of supplying electrical power to a control circuit of acell switch on the basis of at least one cell of the photovoltaic energygeneration device.

The method for managing a photovoltaic energy generation device cancomprise a step of supplying electrical power to all the otherelectronic components internal to the photovoltaic energy generationdevice requiring power supply by at least one cell of the photovoltaicenergy generation device.

The method for managing a photovoltaic energy generation device cancomprise a step of communication by carrier current between a processingcircuit of a module and that of another module or a central computer ora load.

The method for managing a photovoltaic energy generation device cancomprise a step of regulating the output voltage of the photovoltaicenergy generation device which comprises a step of opening/closing cellswitches of the photovoltaic energy generation device so as to follow animposed output voltage setpoint.

The method for managing a photovoltaic energy generation device cancomprise a step of disconnecting all the cells of the photovoltaicenergy generation device in case of prolonged shutdown of thephotovoltaic energy generation device or of incident.

The method for managing a photovoltaic energy generation device cancomprise a step of diagnosing the operation of all or some of the cellswitches and/or module switches and/or parallel switches.

The method for managing a photovoltaic energy generation device cancomprise a step of computing the number of subsets of the photovoltaicenergy generation device to be disposed in parallel or in series.

The method for managing a photovoltaic energy generation device cancomprise a step of identifying the characteristics of at least onephotovoltaic cell and/or of the sunshine by opening over a predefinedperiod at least one cell switch so as to measure the no-load voltage ofthe photovoltaic cell or by closing at least one cell switch and aparallel switch or module switch in such a way as to short-circuit thephotovoltaic cell so as to measure the short-circuit current of the saidphotovoltaic cell.

These objects, characteristics and advantages of the present inventionwill be set forth in detail in the following description of particularembodiments given without limiting effect in conjunction with theattached figures among which:

FIG. 1 schematically represents the use of a photovoltaic energygeneration device according to a prior art.

FIG. 2 represents the electrical layout of an elementary photovoltaiccell connected to a load.

FIG. 3 represents the evolution of the current and of the power providedby a photovoltaic cell as a function of the voltage across itsterminals.

FIG. 4 represents the evolution of the current as a function of thevoltage across the terminals of a photovoltaic cell for varioustemperatures.

FIG. 5 represents the evolution of the current as a function of thevoltage across the terminals of a photovoltaic cell for variouslightings.

FIG. 6 schematically represents a photovoltaic energy generation deviceaccording to one embodiment of the invention.

FIG. 7 represents another schematic illustration of the samephotovoltaic energy generation device according to one embodiment of theinvention.

FIG. 8 schematically represents a module of the photovoltaic energygeneration device according to the embodiment of the invention.

FIG. 9 illustrates more precisely the electrical layout chosen forimplementing the module illustrated in FIG. 8.

FIG. 10 illustrates the electrical layout for implementing the moduleillustrated in FIG. 8 according to a variant embodiment.

FIG. 11 represents the physical implementation of the electricalfunctions of the invention in the architecture of a photovoltaic energygeneration device according to one embodiment of the invention.

FIG. 12 illustrates more precisely the components present on eachelectronic card of the embodiment of the invention.

FIGS. 13 a and 13 c illustrate a variant embodiment of the embodiment ofthe invention.

FIG. 14 represents in a more detailed manner the architecture of theelectronic card according to this variant embodiment of the embodimentof the invention.

FIG. 15 illustrates a second variant embodiment of the embodiment of theinvention.

FIG. 16 represents in a more detailed manner the architecture of theelectronic card associated with a module according to this secondvariant embodiment of the embodiment of the invention.

FIGS. 17 a and 17 b illustrate a third variant embodiment of theembodiment of the invention.

FIG. 18 illustrates a variant embodiment of an electronic card of theembodiment of the invention.

FIG. 19 illustrates an embodiment of a frame incorporating aphotovoltaic energy generation device according to the invention.

FIG. 20 illustrates the steps of a method for managing a cell of aphotovoltaic energy generation device according to one embodiment of theinvention.

FIG. 21 illustrates the steps of a method for managing a module of aphotovoltaic energy generation device according to one embodiment of theinvention.

FIG. 22 illustrates the principle of driving a parallel transistoraccording to one embodiment of the invention.

FIG. 23 illustrates an embodiment of a slaved control of thephotovoltaic energy generation device according to the invention.

FIG. 24 represents an exemplary voltage which can be provided by thephotovoltaic energy generation device according to the invention.

FIG. 25 represents an embodiment of a photovoltaic energy generationdevice according to the invention exhibiting an H-bridge.

FIG. 26 represents in a more detailed manner the architecture of aphotovoltaic energy generation device exhibiting an H-bridge accordingto one embodiment of the invention.

FIG. 27 schematically illustrates the implementation of the principle ofcommunication by carrier current within the photovoltaic energygeneration device according to one embodiment of the invention.

FIGS. 28 to 30 illustrate three variant embodiments of a photovoltaicenergy generation device with several distinct parallel switchesaccording to one embodiment of the invention.

FIG. 31 illustrates an embodiment of the invention, in which thephotovoltaic energy generation device is separated into several parts.

FIG. 32 represents in a more detailed manner the architecture of aphotovoltaic energy generation device separated into several parts andexhibiting an H-bridge according to one embodiment of the invention.

FIG. 33 represents the architecture of a computer implementing a methodfor managing a photovoltaic energy generation device according to oneembodiment of the invention.

FIG. 34 represents in a more detailed manner a variant architecture of aphotovoltaic energy generation device separated into several parts andexhibiting an H-bridge according to one embodiment of the invention.

FIG. 35 illustrates a solution for the driving of the series andparallel transistors on the basis of a relatively low voltage arisingfrom the cells.

FIG. 36 illustrates a photovoltaic energy generation device comprisingthree columns according to one embodiment of the invention adapted fordelivering three independent voltages with possible inversion of sign.

FIG. 37 illustrates a variant embodiment of the photovoltaic energygeneration device of FIG. 36 adapted for delivering a three-phasevoltage.

FIG. 38 represents in detail an architecture of a photovoltaic energygeneration device delivering a three-phase voltage according to oneembodiment of the invention.

FIG. 39 represents an exemplary operation of the photovoltaic energygeneration device of FIG. 38 delivering a three-phase voltage.

FIG. 40 illustrates an embodiment of the invention enabling cells ofmodules to be placed in series or parallel.

FIG. 41 illustrates a variant of the previous embodiment.

FIG. 42 illustrates another embodiment of the invention enabling cellsof modules to be placed in series or parallel.

FIG. 43 illustrates a variant of the previous embodiment.

FIG. 44 illustrates the elements for management of the variant of theprevious embodiment.

FIGS. 45 and 46 illustrate another embodiment of the invention enablingcells of modules to be placed in series or parallel.

In the subsequent description, the photovoltaic cell taking the form ofan indissociable assembly of minimum surface area for photovoltaicenergy production will be called an elementary photovoltaic cell 2.

A set of one or more elementary photovoltaic cell(s) will be called aphotovoltaic cell 7. In the case of a multitude of elementaryphotovoltaic cells, they will be able to be associated according to anyelectrical layout, in series and/or parallel, in such a photovoltaiccell. Next, the association of a photovoltaic cell 7 with an electricalstorage element 8, linked to its terminals, which can be of any type,for example capacitive, will be called a cell 11.

In the following figures, the same references will be used for identicalor similar elements in each embodiment of the invention, for the sake ofsimplifying the description.

FIG. 2 schematically represents the electrical circuit equivalent to anelementary photovoltaic cell 2 linked to a load 15. FIG. 3 representsthe curve 3 of evolution of the current I at the terminals of theelementary photovoltaic cell as a function of the voltage V, as well asthe curve 4 of evolution of the power provided by the elementaryphotovoltaic cell, defined by the formula P=V×I as a function of thevoltage V. It follows therefrom that there exists an optimal operatingpoint P_(opt), for which the power provided by the elementaryphotovoltaic cell, defined by the formula P_(opt)=U_(opt)×I_(opt), is amaximum. As recalled in the preamble, photovoltaic energy generationdevices comprise numerous photovoltaic cells which do not all operateunder these optimal operating conditions. The embodiments of theinvention which will be described make it possible to improve thephotovoltaic energy generation performance in particular by allowing amaximum of elementary photovoltaic cells to operate at or in proximityto their optimal operating point.

As a supplement, FIG. 4 illustrates four curves 3 a, 3 b, 3 c, 3 d ofevolution of the current I at the terminals of the elementaryphotovoltaic cell as a function of the voltage V for respectively atemperature of the cell equal to 0° C., 25° C., 50° C. and 75° C. Thisfigure shows that these curves depend on the temperature, and it followsfrom this that the optimal operating point mentioned hereinabove alsodepends on the temperature.

FIG. 5 illustrates four curves 3 a′, 3 b′, 3 c′, 3 d′ of evolution ofthe current I at the terminals of a photovoltaic energy generationdevice as a function of the voltage V for respectively four differentilluminations. Curve 3 d′ represents a maximum illumination of 1000W/m², whereas curve 3 a′ represents the curve for an illumination of 800W/m² for the device as a whole. Curves 3 b′ and 3 c′ representintermediate situations for which just a part of the surface of thephotovoltaic energy device receives only 800 W/m² and not 1000 W/m², forexample when a part of the device is shaded, this part being moreconsiderable in the case of curve 3 b′ than in that of curve 3 c′.

FIG. 6 schematically represents an embodiment of the invention in whicha photovoltaic energy generation device comprises a multitude of cells11, formed by a photovoltaic cell 7 and a storage element 8, organizedinto several modules 12 or stage. Moreover, each cell 11 is associatedwith its own switch 13, disposed in series, which makes it possible todisconnect the cell from the remainder of the photovoltaic energygeneration device by its opening: accordingly, we shall call it a “cellswitch 13” subsequently. Moreover each module 12 also comprises a switch14 in parallel with the cells 11 of the module 12, thus making itpossible to short-circuit the module as a whole: accordingly, we shallcall it a “module switch 14” subsequently. The use of such a structurefor a photovoltaic energy generator makes it possible to circumvent theintermediate converters used in the prior art, for example for a linkwith the mains 5, as is apparent in this FIG. 6. This manner ofoperation will be explained subsequently.

FIG. 7 also schematically represents the same embodiment of theinvention, in which the representation of the cell 11 has beensimplified with respect to FIG. 6. This simplification will be retainedin the following figures so as to streamline them. The cell 11 does,however, retain the same structure as that described hereinabove.Moreover, the energy generation device is illustrated here in adifferent use, to supply a load 15, such as a motor. In this variant ofuse, neither is there any need for an intermediate converter between theenergy generation device and the load 15.

According to an advantageous aspect of the invention, one or moremeasurement sensors are incorporated at the level of all or some of thecells of the photovoltaic energy generation device, in addition to theswitch represented, so as to make it possible, by way of a controldevice for these switches, to use or not use certain cells as a functionof their state and of the needs, as a function of the measurementsperformed. This allows optimization of the photovoltaic energygeneration device.

FIG. 8 illustrates in greater detail a module 12 of the photovoltaicenergy generation device according to the embodiment of the invention.It comprises a lower terminal 17, linked to a lower neighbour module,and an upper terminal 18 for a series link with the upper neighbourmodule. According to this example, this module comprises six cells 11disposed in parallel. Naturally, it could as a variant comprise anyother number of cells. More precisely, the module firstly comprises sixparallel branches disposed between its upper 18 and lower 17 terminals,on which are disposed a cell 11 and a cell switch 13, which is able todisconnect or not disconnect the cell from one of the two terminals 17,18. It comprises a seventh branch on which is disposed a module switch14, in parallel with the cells, able to shunt the cells. In the exampleillustrated, only the third and fourth cells are used since theirrespective cell switches 13 are closed, whereas all the other cellswitches are open. Moreover, the module switch 14 is open so as to placethe module 12 in its normal operating configuration.

FIG. 9 illustrates more precisely the electrical layout chosen forimplementing the layout explained hereinabove, with reference to FIG. 5.In this FIG. 9, only two cell switches 13 are represented so as tosimplify the figure. The various switches 13, 14 are embodied with theaid of power transistors 23, 24, preferably transistors of NMOS type,which afford a gain in conductivity in their passing state with respectto PMOS transistors which could as a variant be used. As a variant, itis also possible to use other types of transistors such as bipolars,FET, JFET, IGBT, etc. It is also possible to place several transistorsin parallel so as to better ensure the passage of the current.Naturally, there therefore exist at least as many cell transistors 23 ascell switches 13, and a module transistor 24 to form the module switch14. All these transistors 23, 24 are associated with diodes 25, 26mounted in parallel, which are incorporated into the transistors if theyare NMOS discrete power transistors or as a variant are distinct diodes,to represent their characteristic of allowing the current to pass in thereverse direction. Finally, a control circuit 27, generally called a“driver”, is supplied electrically through links 28 allowing it torecover a voltage difference corresponding substantially to the voltageof the cell of largest voltage, slightly decreased by a voltage drop(for example close to 0.6 V) at the level of the diodes 40 disposed onthe links 28. The function of this control circuit is to generatecontrol signals 41 towards the various transistors 23, 24 to actuatethem, thus fulfilling a function of control of the switches. In asimilar manner, not represented for reasons of clarity of the figures,all the electronic components of the module can be supplied according tothe same solution, such as a computer making it possible to estimate thestate of the switches, an optional communication system, etc.

The manner of operation of this device will now be explained. During itsuse in a circuit similar to that of FIG. 7, in the customary operatingconfiguration, at least one of the cell transistors 23 is closed,whereas the module transistor 24 is open, thereby allowing the cells 11associated with the closed cell transistors 23 to deliver a voltage anda current which passes through the closed transistors and which willultimately contribute to the power supply for the load 15. A currentflows from the lower terminal 17 to the upper terminal 18. On the otherhand, if all the cell transistors 23 are open and the module transistor24 is closed, the current will pass through this module transistor andthe cells of the module are isolated, do not participate in thegeneration of the supply current. In the case where all the transistors23, 24 are open, the current of the photovoltaic energy generationdevice, will pass through the reverse diode 26 associated with themodule transistor 24, and the voltage across the terminals 17, 18 of themodule remains equal to about −0.6 V (the voltage of the upper terminal18 is about 0.6 V lower than that of the lower terminal 17: this voltagedrop originates from the reverse diode 26 associated with the moduletransistor 26). Finally, it is avoided to position a cell transistor 23closed while the module transistor 24 is also closed, so as not toshort-circuit the cell 11, for safety reasons. Thus, for any passage ofthe cell transistors 23 that are closed to a situation where the moduletransistor 24 is closed, or vice versa, there will preferably beundertaken an intermediate step of opening all the transistors, for ashort period of a few nanoseconds for example.

Moreover, upon the opening of a cell switch, the storage elementassociated with the photovoltaic cell will charge, while enabling thephotovoltaic cell to be maintained around its optimal operating point.

It is beneficial to note that the voltage of a module remains low, evenwhen all the transistors are open, thereby making it possible to useinexpensive transistors supporting relatively low voltages, and whoseresistance in the passing state is very low, thereby inducing fewlosses. This will hold true in particular if the cells 11 exhibit avoltage of less than 40 V.

FIG. 10 illustrates a variant embodiment of the previous electricallayout for implementing the same principle differently, making itpossible in particular to obtain a local power supply for the electroniccomponents 148 of the circuit on the basis of the voltage stored by thecells of the module considered, or indeed of a neighbour module. For thesake of simplification, the electronic components are not detailed, butthey comprise at least one control circuit and switches, as explainedhereinabove. In this variant, a bipolar PNP transistor 149 is associatedwith each cell 11 of the module. All these transistors 149 arecontrolled by one and the same current of a terminal 142 of a controldevice 145. This results, at the output 143 of each transistor, in acurrent whose strength depends on the voltage of each cell 11, that isto say on the state of each cell 11. These currents are added togetherso as to power the electronic components through a resulting current144. The control of the transistors 149 is such that the final supplycurrent 144 attains a desired value. The solution makes it possible toinvoke the various cells of the module as a function of their state, oftheir available voltage.

This solution avoids moreover having the voltage drop between thevoltage available at the level of the module and that actuallyutilizable by the electronic components, as in the embodiment describedhereinabove with reference to FIG. 9, on account of the use of diodes.This voltage drop may in particular be troublesome in an embodiment forwhich the cells were low-voltage cells, of value 1.5 V for example.

The control device 145 comprises an amplification device comprising twoamplification stages 146 and 147 according to this embodiment so as tomake it possible to implement the control of the power supply devicedescribed hereinabove without requiring too considerable a power, whichwould engender a voltage drop at the level of the module, this beingavoided in this embodiment. Accordingly, a first very low current istapped off from the module, at the level of a first transistor Tdiff,and then amplified by an amplification cascade, so as to attain thedesired control value on the terminal 142. The control current on theterminal 142 adjusts itself automatically as a function of the demand interms of current of the electronic components 148, thereby limiting itto what is strictly necessary and in real time and thus limiting themean consumption related to this control.

The numerical values illustrate an exemplary implementation making itpossible to attain a supply current of 40 A by tapping off a current of125 nA for its control.

According to the embodiment of the invention, each cell moreovercomprises at least one sensor for measuring a quantity characteristic ofthe state of the cell. This measurement sensor can for example measurethe voltage and/or the current and/or the temperature at the level ofthe cell concerned. Each measurement sensor is moreover linked by acommunication device to an intelligent device, local and/or remote, suchas a computer of microcontroller type, which receives the measuredvalues and implements a method for managing the photovoltaic energygeneration device, which will be described in greater detailsubsequently, so as to determine an optimized mode of operation of thephotovoltaic energy generation device, by taking account of themeasurements performed. This optimized operation in fact consists indetermining the switches 13, 14 which have to be open and closed. Thisconfiguration of the various switches of the photovoltaic energygeneration device can be modified in real time. This solution thus makesit possible for example to discard the defective cells, to steer thecurrent within the heart of each module, to balance each of the cells ofthe photovoltaic energy generation device in real time. As a remark, themean current demanded by a load 15 powered by the photovoltaic energygeneration device is in general much lower than the peak currentdemanded during heaviest consumption, thereby allowing the photovoltaicenergy generation device to operate satisfactorily most of the time witha relatively considerable number of disconnected cells, that is to saywhose associated cell switch 13 is open, or indeed of disconnectedmodules, that is to say whose associated module switch 14 is closed, iffor example a module is considered to be defective as a whole.

FIGS. 11 to 13 represent possible examples of physical embodiment of theelectrical functions added by the invention in the architecture of aphotovoltaic energy generation device according to one embodiment of theinvention.

FIGS. 11 and 12 illustrate a first embodiment in which an electroniccard 20, which comprises the components explained previously, is addedfor each module of the photovoltaic energy generation device. Thiselectronic card takes the form of a printed circuit positioned under thesurface of each module, under the photovoltaic cells 7, which thusfulfil a function of protecting the electronic cards against outsideassault, such as originating from dirt, rain, etc. Thus, thephotovoltaic energy generation device comprises an electronic card 20for each module. The boards of photovoltaic cells can be pluggeddirectly into the electronic card 20 via connectors or have solderedelectrical connections, so as to electrically link the photovoltaiccells to the electronic cards through connections 38. The storageelements, not represented, can extend under a considerable portion ofthe photovoltaic surface or simply take the form of a component ofreduced size soldered onto the electronic card according to use (simplefiltering of the voltage or mass storage). The electronic cards 20 canbe incorporated into the photovoltaic panel or be attached to thesupport structure of the photovoltaic panel. For example, in the case ofincorporation into a roofing supported by a framework, the electroniccards 20 can be disposed and fixed on the framework battens or rafterswhich will bear the photovoltaic panels which serve at the same time ascovering for the roofing.

Thereafter, according to the embodiment represented in FIGS. 11 and 12,each electronic card is linked by a communication bus 21 to a centralcomputer 22, which receives the measurements performed locally within amodule of the photovoltaic energy generation device and implements amethod for managing the photovoltaic energy generation device,comprising in particular the transmission of commands for opening and/orclosing the switches of the photovoltaic energy generation device. Thistransfer of data by the communication bus 21 may require optionalmultiplexing and digitization of the data, as well as galvanic isolation(by transformer or optocoupler). Moreover, a control circuit 27 isplaced on each electronic card and constitutes an intermediate elementbetween the computer 22 and the switches, allowing the adaptation of thevoltage transmitted to the transistors 23, 24 forming the function ofswitches for the implementation of the commands of the computer. Thesecontrol circuits 27 can moreover incorporate safety functions so as toavoid for example closing a module switch 14 while the cell switches 13are closed, to avoid any short-circuit.

FIG. 12 illustrates more precisely the components present on eachelectronic card, which comprises measurement sensors 29, for measuringthe temperature, the voltage, and the current, one or more processingcircuits 30 for estimating the state of each cell for example,determining the relevance of using or not using each cell, etc. Theelectronic card 20 moreover comprises a control circuit 27 allowing theactuation of the various transistors 23, 24, forming the switches 13,14. Finally, it comprises a communication interface linking with thecommunication device so as to communicate with the central computer 22.

FIGS. 13 a and 13 b illustrate a variant embodiment in which theelectronic functions of each electronic card of the embodiment describedhereinabove are grouped together on a single electronic card 20, towhich the cells are linked electrically by connections 38. FIG. 13 arepresents a view from underneath, making it possible to see thedistribution of the modules 12 on the card 20. In the case ofincorporation into a roofing supported by a framework, the electroniccard 20 can be disposed and fixed on a batten or a rafter of theframework, which will bear the photovoltaic panels which serve at thesame time as covering for the roofing. The card 20 can be split intoseveral pieces and stretch over several battens or rafter 42 of theroofing, as is apparent more particularly in FIG. 13 c, and these piecescan be linked electrically by cables like the communication bus 21 and apower cable 47 for placement in series. To ensure the leaktightness ofthe roof, the photovoltaic panels can rest on a support such that aleaktight overlap exists between the panels. During the construction ofthe support structure of the installation, such as a framework,provision may be made on the card 20 for a photovoltaic cells wiringnumber that is greater than the number of photovoltaic cells installedat the outset so as to be able in the future to increase the number ofphotovoltaic cells of the installation. The photovoltaic cells notinstalled at the outset will simply be shunted by the module switch.

FIG. 13 b represents a rear perspective view, making it possible todistinguish various photovoltaic cells 7, as well as certain electroniccomponents like cell transistors 23, represented summarily in anon-exhaustive manner so as to simplify the representation of theelectronic card 20 disposed under the surface of the photovoltaic cells,opposite from their upper face receiving a light flux 39. The electroniccard 20 comprises all the components explained previously. Thecommunication bus 21 extends over the entire length of the card as faras the central computer 22, positioned towards a free end of theelectronic card 20. This communication bus 21 can be physically isolatedfrom the electronics of the modules by establishing a printed-circuitband dedicated to the communication bus, separated from the electroniccomponents of the various modules, by separating for example theirearths, and/or by maintaining a safety distance between the two parts.Only the elements for communication between these two parts, such astransformers or opto-couplers, will remain straddling these two parts toensure communication while guaranteeing galvanic isolation.

FIG. 14 represents in a more detailed manner the architecture of theelectronic card 20 associated with two modules 12, each comprising sevencells in this example. For each cell, a cell transistor 23 is provided,in series with the cell, and a module transistor 24, in parallel, isprovided for each module 12, as explained previously. Moreover, atemperature sensor 33, a voltage sensor 35 and a current sensor 36 areprovided for each cell. The measurements performed by these threesensors 33, 35, 36 are transmitted to a local processing circuit 30 viaa multiplexer 32 by respectively three communication pathways 43, 45,46. As a remark, the connections have been simplified in the figures forthe sake of clarity, but there is in reality a ribbon of wires to obtaina connection to each sensor and to each voltage. Moreover, the voltageof the module is also advantageously measured so as to deduce therefromthe voltages present at the level of the transistors. The processingcircuit 30 thus receives these data at the level of a communicationinput 31 performing a digitization, of “ADC input” type; or as avariant, these signals arrive already digitized, this digitization beingcarried out at the level of the multiplexer 32. According to a possibleembodiment, the processing circuit 30 can be a microcontroller having anumber of input/output sufficient to interrogate the assembly ofsensors. All the transistors 23, 24 are driven by a power controlcircuit 27 which transmits control signals 41 to them, under the ordersof the processing circuit 30. Finally, the processing circuit 30 islinked to the central computer 22 by the communication bus 21 and by wayof an interface 37 forming a galvanic isolation. All these componentsassociated with a single module are supplied through the voltage of atleast one of the cells of the module 12. As has been described, eachmodule 12 of the photovoltaic energy generation device has its ownintelligence by virtue of its processing circuit 30 and thusparticipates in the method for managing the photovoltaic energygeneration device, in cooperation with the central computer 22 whichdrives the assembly of modules. Said computer will be described ingreater detail subsequently, with reference to FIG. 23.

Moreover, according to an advantageous embodiment, all the powercomponents associated with a module are supplied directly through thevoltage available at the level of the corresponding module, inparticular the control circuit 27 for the transistors, describedpreviously. Such a control circuit, powered by its associated module, isthen electrically isolated from the other modules and/or the electricalpotentials outside the module. Such an embodiment exhibits the advantageof eliminating the risk of driving a certain transistor with a verydifferent potential from that of the stage, which could lead to itsdestruction or to its short circuiting. Moreover, this solution affordsthe additional advantage of allowing a reduction in the connectionsbetween the components of the control circuit and the power supplysource, since it is possible to group them together a short distancefrom one another and from the voltage source, in particular bypositioning the transistors as close as possible to the cells to beconnected. Finally, the use of very short connections also greatlyreduces any risk of short-circuit, for example between two modules.

Likewise, a communication device powered by the stage can make itpossible to communicate with the other stages and/or with a centralsystem via a highly insulated tie to avoid electrical risks (shortcircuits between stages, deterioration of the central system placed at apotential differing greatly by a few kV from that of a stage of thephotovoltaic energy generation device, electrical risk for therepairer). In contradistinction to a pulse transformer which would makeit possible to control the power transistors through a galvanicisolation, the use of a communication device powered by the module makesit possible to interpret the signals received (decoding of the address,of the information), to code the signals to be transmitted and to poolthe communication lines whereas the pulse transformer makes it possiblemerely to set the power transistor “on” or “off” with an individualizedconnection line to each transistor. The communication device may forexample be an I2C interface present in numerous microcontrollers, thatis read back to a pooled communication bus for each stage via a galvanicisolation.

In the example described hereinabove, the method for managing thephotovoltaic energy generation device is implemented through thecooperation of a local processing circuit 30, disposed at the level ofeach module, and of a central computer 22. All of the photovoltaicenergy generation device management functions will therefore be able tobe implemented by this combination. Several embodiments can thus becontemplated, by shifting certain management functions from the locallevel to the central level or vice versa.

FIGS. 15 to 17 illustrate a second variant embodiment in which themethod for managing the photovoltaic energy generation device isimplemented locally only, at the level of each module, or indeed cell.This exhibits the advantage of allowing more reactive driving of thevarious switches, of avoiding the obligation to provide galvanicisolation between the electronic cards 20 and a central computer 22 andcomplex coding of the information to be transferred. FIG. 15 illustratessuch a variant, in which each electronic card 20 comprises measurementsensors 29, for measuring the temperature, the voltage, and the current,one or more processing circuits 30 for estimating the state of each cellfor example, determining the relevance of using or not using each cell,etc. The electronic card moreover comprises a control circuit 27allowing the actuation of the various transistors 23, 24, forming theswitches for cell and module.

FIG. 16 represents in a more detailed manner the architecture of theelectronic card associated with a module 12, comprising six cells inthis example. For each cell, a cell transistor 23 is provided, disposedin series with the cell, as has been explained previously. Furthermore,a temperature sensor 33, a voltage sensor 35 and a current sensor 36 aremoreover arranged at the level of each cell. The measurements performedby these three sensors 33, 35, 36 are transmitted to a processingcircuit 30 via a multiplexer 32 through respectively three communicationpathways 43, 45, 46, or as a variant through one and the same pooledpathway. The processing circuit 30 thus receives these data at the levelof a communication input 31 performing a digitization, of “ADC input”type. According to a possible embodiment, the processing circuit 30 canbe a microcontroller having a sufficient number of input/output tointerrogate all of the sensors. As a remark, the single moduletransistor 24 is replaced in this embodiment by several parallelswitches formed by transistors 34: in this variant, a paralleltransistor 34 is disposed in parallel with each cell so as to reduce toa minimum the length of the power paths when these transistors 34 areactivated. Thus, it is apparent that in all the embodiments and theirvariants, the module switch 14 can be replaced with parallel switches 44on each cell of the module, or indeed by any number of parallelswitches, such as a parallel switch for one or two cells. All thesetransistors 23, 34 are driven by a control circuit 27, under the ordersof the processing circuit 30.

FIGS. 17 a and 17 b illustrate a third variant embodiment, which is akinto that of FIGS. 13 a and 13 b, in which the electronic functions aregrouped together on a single electronic card 20, and for which only alocal processing at the level of each module is performed, without anylink with a central computer. FIG. 17 a represents a view from above,making it possible to see the distribution of the modules 12 on the card20, whereas FIG. 17 b represents a rear perspective view, making itpossible to distinguish various cells 11, as well as certain electroniccomponents such as cell transistors 23, represented summarily in anon-exhaustive manner so as to simplify the representation of theelectronic card 20. However, the latter comprises all the componentsexplained with reference to FIG. 16.

As a remark, it is ultimately possible to effect embodiments withvarious numbers of electronic cards 20, a card being able to contain theelectronic circuits of the invention for one, two, or any number ofmodules. Moreover, it is also possible to provide for other embodimentsin which part only of the electronic components presented previously arepresent, on an electronic card or not, or in which certain componentsare shared between cells and/or modules. For example, a circuit forcontrol of switches and/or a processing circuit can be shared by severalneighbour modules, for example for two or three neighbour modules, so asto retain an acceptable voltage supply.

In all cases, the electronic cards 20 are advantageously disposed insuch a way as to dispose their connection terminals with the cells 11 asclose as possible to the terminals of the cells so as to reduce to themaximum the length of the connections and therefore the associatedlosses. Likewise, on the printed circuit of the electronic card, thepower paths are as short as possible with the highest possible conductorcross-section.

To increase the conductor cross-section, it is possible to strengthenthe tracks of the printed circuit by soldering above a conducting wireor baton. FIG. 18 illustrates such a solution, in which an electroniccard 20 of printed circuit type is overlaid on a module of several cells11. In this figure, only two modules of two cells are represented, forthe sake of clarity of the figure, but the photovoltaic energygeneration device comprises more than two modules each having more thantwo cells. As a remark, such a strengthening can fulfil the secondfunction of evacuating the heat generated, in particular that dissipatedby the power transistors; accordingly, its shape can exhibit a surfacefavouring this function, in the manner of a convector or radiator.Connectors 16 are rigged up on this board, so as to link the cellselectrically to the electronics of the card (for example cells whosepositive and negative terminals pass through the card and clamp the cardand the strengthened power tracks via a nut which is screwed onto theterminals of the cell. A relatively elastic washer can be added betweenthe card and the nut to compensate for the effects of thermal expansionand ensure good electrical contact over the duration. As a variant,simple soldering can ensure the electrical contact between the terminalsof the cell and the power tracks of the PCB card. As is apparent in thefigure, electrical conducting strengtheners 19 are added to the tracksof the printed circuit. These strengtheners also represent a potentialthermal radiator soldered and/or glued to the tracks. As a supplement,holes, not represented, can be made through the electronic card 20 tofacilitate the circulation of air and the cooling of the cells 11 andelectronic components.

Ultimately, the structure thus described of a photovoltaic energygeneration device is of modular type, and allows a physicalimplementation in the form of various independent and removablehousings, which each correspond to a set of cells and therefore eachcomprise several elementary photovoltaic cells, which can be connectedtogether, by way of a communication bus and of a power bus. Each housingcan comprise an arbitrary sub-part of the overall device, which canrange from one module to several modules.

FIG. 19 schematically illustrates such an approach in which the varioushousings 150, each comprising photovoltaic panels of severalphotovoltaic cells, are linked by a removable link to a communicationbus 152 by way of a connector 153, in a highly galvanically isolatedmanner, and to a power bus 151 by a power connector 154 which allowsthem a series link with the adjacent housings. A locking/unlockingdevice 158 is associated with a switch system making it possible toautomatically cut the connections to the communication bus and to thepower bus when it is actuated to remove a housing 150. The connection isreplaced with a short-circuit, via for example the mechanical orelectrical switch 155, when the housing is removed so as not to cut theconnection between the remaining housings. Accordingly, a start oflocking or of unlocking by actuation of a lever or handle of thelocking/unlocking device is detected and an item of information istransmitted to the device's global management system, such as a centralcomputer. In the case of unlocking of a housing, the computer discardsit immediately from the overall operation of the device and imposes onit a zero voltage across its terminals, thereby ensuring the safety ofthe future manipulations and allowing its secure storage. Theconnections with the power and communication buses are thereafterautomatically cut, by a switch, in a mechanical or electrical manner.The previous operations are performed in a reversible manner in case ofintroduction of a housing into the frame.

This construction exhibits the advantage of simplified physicalmanagement of the photovoltaic energy generation device. Each subsetincluded in each housing is managed in an independent orsemi-independent manner by virtue of the architecture described in theembodiments presented previously. It is thus possible to preciselyascertain the state of each housing, and to be able to intervene on agiven housing in case of failure, so as to change a module or indeed acell, or to be able to exchange it if necessary, without penalizing thewhole device.

This physical assemblage can thus be disposed on the framework of abuilding, the various housings being distributed on the surface of theroof. This architecture makes it possible to easily add or removesubsets, i.e. photovoltaic panels, to or from the overall device, whoselinking and management is thereafter carried out automatically in anoptimal manner. It therefore makes it possible to afford user-friendlyand convenient upgradability of a photovoltaic energy generation device.

The invention also pertains to a method for managing a photovoltaicenergy generation device such as described previously. This methodconsists in optimizing the power produced by the device while complyingwith a first constraint imposed by the available sunshine and a secondconstraint related to the specific demand of the load connected to thedevice. Naturally, the first constraint takes priority over the secondin case of incompatibility, since the photovoltaic energy generationdevice is automatically bound in its production capacity to sunshine,this implying that in the worst case, it will not be able to satisfy aneed going beyond its maximum capacity.

The photovoltaic energy generation method comprises a step consisting indetermining the position of the cell switches as a function of theoperating state of the photovoltaic cells concerned, more precisely as afunction of their state with respect to their optimal regime.Accordingly, when the voltage across the terminals of a cell exceeds theoptimal voltage, presented previously with reference to FIG. 6,increased by a predefined percentage, the cell is then used in apriority manner, that is to say its cell switch is closed so as to allowits use to produce a voltage and a current towards the output of thedevice. This use of the cell, which induces provision of a current bythe photovoltaic cell and by its associated storage element, tends tocause the voltage across the terminals of the photovoltaic cell todecrease, thereby preventing this voltage from climbing too far andstraying too far from the ideal operating voltage. On the contrary, whenthis voltage across the terminals of a cell falls below this optimalvoltage decreased by a predefined percentage, the cell is then no longerused, that is to say the cell switch is opened, so that said cell nolonger participates in the production of voltage and current at theoutput of the device. During this disconnection of a cell from theremainder of the device, its energy production is utilized for chargingthe storage element which is associated therewith and the voltage acrossits terminals rises. This mechanism, illustrated by FIG. 20, thuscomprises the setting up of cycles of opening and closing of the cellswitch 13, as represented by the curve 53, as a function of the state ofthe associated cell, that is to say of the operating conditions of itsphotovoltaic cell 7 with respect to the optimal conditions, so thatthese operating conditions always remain in a range close to the idealconditions, preferably in a range of plus or minus 5% of the optimalconditions, advantageously of 2.5% of these conditions. Thisoptimization can be done on each elementary photovoltaic cell in thecase where each is individually associated with a cell switch, that isto say in the case where a photovoltaic cell 7 comprises just a singleelementary photovoltaic cell. As a variant, this optimization can bedone on several elementary photovoltaic cells. Curve 54 represents thestate of the parallel switch 44 associated with the cell considered,which is open when the cell switch 13 is closed and vice versa. Curve 52illustrates the current i at the terminals of the photovoltaic cell 7,which forms step changes similar to those of curve 53: the current takesa non-zero value upon the closing of the cell switch, illustrated by the“ON” label of curve 53, for the periods T1, T2 represented. During theseperiods, the photovoltaic cell 7 is used and its voltage V falls as isvisible on curve 50, before rising when the cell switch is opened. Thevoltage V across the terminals of the photovoltaic cell 7 does indeedoscillate around the optimal voltage V_(opt). The voltage Vmodule acrossthe terminals of the module, represented by curve 51, takes a zero valuewhen the cell switch 13 is open, since the cell is shunted by theparallel switch 44 which is closed, and then a value equal to that ofthe cell during the periods T1, T2 of use of the latter.

As a remark, disconnecting a cell of lower voltage from the remainder ofthe device, whether this is because this cell is situated in a shadedzone or for any other reason, makes it possible to avoid it also havinga harmful influence on all the other cells, which can be more easilymaintained in their optimal operating state. Indeed, a shaded cell wouldrun the risk of behaving as a load in relation to the remainder of theenergy generation device, and therefore of dissipating energy producedwhile running the risk of overheating and of necessitating a reductionin overall current provided in order to reduce this risk.

This method of photovoltaic energy generation management thereforecomprises a step of determining the operating conditions of aphotovoltaic cell.

Accordingly, the method comprises a step of measuring at least onequantity at the level of a cell of the photovoltaic energy generationdevice, representative of the state of the cell, such as the voltageand/or the current, and optionally the temperature. As a remark, this orthese measurements are advantageously performed locally, by one or moresensors, as mentioned previously.

According to a first embodiment, only the voltage across the terminalsof the cell is measured. The current can be deduced by analysing thevariation in voltage across the terminals of the storage element in aphase of charging of this element, when the cell switch 13 is open,since this current is related to the voltage. For a capacitance C, thecurrent is related to this voltage by the well known formula of i=CdV/dt.

Thereafter, this (or these) measurement is utilized by a computer of aprocessing circuit, which is advantageously local, that is to saypositioned for example on an electronic card in proximity to the cell,as has been described previously. As a variant, the measured quantity istransmitted to a central computer.

This computer implements a method for comparing the actual state of thecell with an optimal operating state, on the basis of this measurement.Accordingly, a first embodiment is based on the prior storage of theoptimal values in an electronic memory associated with the computer,such as the storage of the optimal operating voltage as a function oftemperature for example. A second embodiment is based on the periodicsearch, optionally in real time, for the optimal operating conditions.Accordingly, a solution can consist in letting the operating conditionsof a cell evolve slightly so as to verify whether or not this isaccompanied by an increase in the power provided by the cell. If thepower increases, then the evolution is continued in the same direction.On the other hand, if it decreases, the reverse evolution is set up.This principle ends up culminating through successive iterations at theoptimal operating point and then making it possible to continue themanagement method described previously, so as to remain around thispoint.

Ultimately, the method for managing an energy generation devicetherefore comprises the implementation of the following steps:

-   -   transmission of the measured quantity to at least one computer;    -   determination of the position of a cell switch and/or module        switch by taking into account the measured quantity;    -   transmission of a command for opening or closing a cell switch        and/or module switch as a function of the preceding        determination.

The photovoltaic energy generation device management method thus makesit possible to determine at each instant the position of severalswitches of cells and/or modules, so as to maintain each cell and moduleunder optimal conditions.

The method can moreover comprise an intermediate step consisting indiagnosing a failure and/or an at-risk state of a cell, by recognizingdefective cells, for example overheating subsequent to a situation ofshort-circuit, ingress of moisture, electrical arcing, flame, isolationdefect, etc., on the basis of the quantity measured at the level of acell, so as to disconnect or discard from the overall operation of thephotovoltaic energy generation device the cells concerned, by openingfor example their cell switch, or by closing the module switchconcerned.

Thus, returning to the example illustrated in FIG. 8, it is apparentthat cells 1, 2, 5, and 6 have been discarded. In a photovoltaic energygeneration device comprising a considerable number of cells and modules,it is easy to discard a significant number of them, for example 10% ofthe total number of cells, without penalizing the use of thephotovoltaic energy generation device since the current demanded isgenerally less than the maximum current available, used solely in asituation of consumption peak. Otherwise, in case of a spike inconsumption, it will always be possible to call momentarily upon thediscarded cells to meet the more considerable need.

As a remark, in case of a spike in current, the storage elementsassociated with the cells also deliver a current complementary to thatproduced by the photovoltaic cells, thus participating in the overalloptimization of the energy production since the energy produced by thecells, even while they are disconnected, is ultimately utilized. Thestorage elements thus fulfil a buffer role, allowing the retrieval witha stagger of all the energy produced under optimal conditions. They alsoavoid overly heavy variations in voltage across the terminals of thecells during the operations of connection and disconnection by actuationof their cell switch, allow continuous evolution of their voltage.Accordingly, they are sized so as to maintain a weak variation in thevoltage across the terminals of the cell relative to its continuouscomponent ΔV/V, for example less than 5%, thereby allowing a cell toremain close to its optimal conditions, its voltage variation remainingnegligible.

The photovoltaic energy generation device management method comprises astep of diagnosing a cell including a step of estimating the state of acell, which can comprise by way of nonlimiting example one or moremeasurements of current, voltage, temperature, impedance spectrometry orthe like at the level of at least one cell, all or some of the cells ofthe photovoltaic energy generation device. Accordingly, the measuredquantity can be compared with predefined thresholds. The driving of eachcell transistor then depends on this estimated state of the cell, andmakes it possible for example to disconnect a cell if it causes anabnormal temperature or a current to appear or if it provides a currentwhich is the reverse to the other cells.

This diagnosis step can comprise the identification of thecharacteristics of at least one photovoltaic cell and/or of the sunshineby opening over a sufficiently long predefined period at least one cellswitch so as to measure the no-load voltage of the photovoltaic cell orby closing at least one cell switch and a parallel switch or moduleswitch in such a way as to short-circuit the photovoltaic cell so as tomeasure the short-circuit current of the said photovoltaic cell.

The method for managing the generation of photovoltaic energy has beendescribed for optimizing the operation of a particular cell of thedevice. However, the various cells of the device are interdependent andit is useful to also consider them in a global manner.

In particular, it is advantageous to avoid imbalances within one and thesame module without which it will not be easy to keep all the cells ofthe module in their optimal operating condition. Such an imbalance canfor example arise if part of the cells is shaded for example. In such acase, the storage elements associated with these various cells arecharged at different speeds and the voltages across the terminals ofthese cells can differ, when the cell switches are open. To compensatethese imbalances, the management method can apply the principledescribed previously, in conjunction with FIG. 20, but in atime-staggered manner for each cell.

FIG. 21 illustrates more precisely a possible embodiment forcompensating the imbalance of three cells of one and the same module. Atan instant t1, the voltage across the terminals of the first cell,represented by the curve 55, attains a threshold value beyond itsoptimal operating voltage, and its cell switch passes from the open toclosed state, to use the cell. The voltage of the module, represented bythe curve 58, then passes from a zero value to the value of the voltageof this first cell. The other two cells which are in shaded positions,and whose voltage is lower, remain unused and their voltage continues toincrease, while that of the first cell decreases. The voltage of themodule, represented by the curve 58, then decreases, like that of thefirst cell. At the instant t2, the voltage of the module becomes closeto that across the terminals of the third cell, represented by the curve57, and the cell switch of the latter passes from the open to closedstate. Likewise, at the instant t3, the voltage of the module becomesclose to that across the terminals of the second cell, represented bythe curve 56, and its cell switch passes from the open to closed state.At each addition of an extra cell, at the instants t2 and t3, the slopeof the decrease in the voltage of the module is modified, this decreaseslows down because more and more cells contribute to the provision ofthe output current. This progressive connection of the various cellsavoids moreover the risks of short-circuits between the cells, withrespect to a solution which would consist in connecting at the same timethe cells of the module of different voltage. At an instant t4, thevoltage of the module falls below a threshold beneath the optimalvoltage of the three cells and their switches are then openedsimultaneously. The photovoltaic generation device management computerthen takes account of the actual voltage of each cell, of their optimalvoltage, and also of the voltage of the module.

In this global approach, the computer can compute one and the sameglobal optimal voltage value per module, by taking account of thetemperature and optionally of the global sunshine. As a variant, it ispossible to compute more precisely an optimal voltage value specific toeach module, by taking account of the temperature and optionally of thesunshine at the level of each module. In this case, each module is usedin a different manner, is turned to account as a function of its ownsituation, like its sunshine, the state of its cells, optionally theirfailure, or indeed their technology if several generations of modulesare used (for example if failed modules have been replaced with morerecent modules, or if an existing installation has been enlarged by theaddition of more recent modules), etc.

Moreover, the photovoltaic energy generation device management methodcan implement a cyclic modification of the use of the cells, so that allor some of the cells of the photovoltaic energy generation device passfrom a normal operating state to a disconnected state and vice versa,according to a determined duty ratio which can be fixed or variable. Theoperating cycles of the various cells can be staggered over time toobtain at each instant a substantially equivalent number of active cellsfor example, guaranteeing at each instant a sufficient number of activecells to satisfy the current demanded.

The solution adopted in fact amounts to determining the output currentof the photovoltaic energy generation device so that the cells operateto the maximum in their optimal operating point. This current is in factdetermined by the sunshine received by the photovoltaic cells. It isimpressed on the load linked to the device. However, numerous means areimplemented to also get as close as possible to the need of this load interms of current and voltage, while remaining under the optimaloperating conditions of the photovoltaic cells, as will be detailedsubsequently.

Thus, the photovoltaic energy generation device management methodimplements the following steps:

-   -   mutual balancing of the modules and/or cells, using by priority        the modules and/or cells whose voltage is the highest when the        photovoltaic energy generation device is connected to a load;    -   balancing of the modules and/or cells by modifying the mean rate        of use of the modules and/or cells, but without using the same        modules and/or cells permanently, so that the voltage of the        modules and/or cells balances.

The implementation of the method for managing the photovoltaic energygeneration device described hereinabove can be implemented by a localand/or remote computer, as has been explained earlier. This computer cancomprise one or more microprocessors.

As a remark, the implementation of the method locally, without recourseto a central computer, exhibits the following advantages:

-   -   as the measurement or measurements and their analysis are done        locally and independently of the other modules, the reaction can        be very fast. It is faster than the embodiment with a central        computer which would require a communication by a link with        galvanic isolation, with firstly a serial coding which would        induce a first lag, and then the transfer by a bus whose        restricted bitrate would involve a second lag;    -   in the case where a module comprises its own computer, a        thorough processing of the measurements can be done, so as thus        to reach a precise diagnosis of each cell.

The photovoltaic energy generation device management method can comprisethe following specific steps in the case where the management of a cellis entirely local:

-   -   as soon as the failure rate of the cells of one and the same        stage attains a threshold, a command orders the opening of all        the cells and the activation of a shunt, potentially placed in        each of the cells, so as to disable the stage;    -   when a cell has failed, for example when there exists a leakage        of current, overheating, when it is overly discharged (this        being for example detected by crossing below a voltage        threshold) or overly charged (this being for example detected by        an overshooting of a voltage threshold or of an acceptable        number of ampere hours), it is disconnected by opening its        series transistor;    -   when a cell heats up, it can be connected/disconnected according        to a duty ratio, in such a way as to limit its temperature rise.        This objective can be achieved by servocontrol of the duty ratio        as a function of the temperature measured at the level of the        cell;    -   if a disconnected cell sees the voltage of the stage fall        sufficiently below 0V (a few −100 mV for example), then it        closes its parallel transistor (no risk of short-circuiting the        cells placed in parallel since the voltage itself crosses        through zero: typically when all the cells of the same stage are        disconnected and a current is consumed on the photovoltaic        energy generation device or when their sunshine/performance is        not sufficient to maintain a positive voltage on the stage). A        small lag can be provided between the detection of the crossing        of the voltage below the threshold and the command of the        parallel transistor so that the neighbour cells have also had        time to detect the crossing of the threshold;    -   upon the application of a recharging current to the photovoltaic        energy generation device, if a disconnected cell sees the        outside voltage rise above the maximum voltage that a cell can        attain on charge, then it closes its parallel transistor (no        risks of short-circuiting the cells placed in parallel since in        order that the voltage can go beyond this threshold, it is        necessary that all the cells of the stage be open);    -   if a cell sees too high a current, and this may in particular        happen when there are no longer enough cells in parallel to        provide the current demanded or to accept the current afforded,        then the series transistor of the cell is opened, thereby        eliminating the risk of deterioration of the cell. If subsequent        to this disconnection, the remaining active cells placed in        parallel see too high a current, they will also disconnect        themselves;    -   when all the cells of a stage are disconnected, and if a current        is consumed on the photovoltaic energy generation device, then        the voltage at the level of the stage will drop and tend to be        negative: at that moment, each of the cells will activate its        parallel transistor which will take over for the flow of the        current in the photovoltaic energy generation device;    -   when all the cells of a stage are disconnected, and if a        recharging current is afforded to the photovoltaic energy        generation device, then the voltage of the stage will rise and        overshoot the maximum charging voltage of a cell: in this case,        the cells will trigger the closure of their parallel transistor;    -   to be certain that all the cells have properly detected the        voltage threshold overshoot, it is possible to intentionally        place a small delay on the control of the parallel switch at the        level of each cell so as to properly allow the voltage to        progress before returning it to zero through this closure;    -   if a cell has disconnected subsequent to too considerable a        discharge (crossing below a voltage threshold), it may decide to        reactivate as soon as the voltage of the stage tends to approach        that of the cell (case where the parallel switch has not been        activated). If the parallel switch had been activated, then the        decision to deactivate it may be made on the basis of a        detection of a current in the shunt, which is in the direction        of a recharging current or of a discharging current that is        below a threshold. The opening of the parallel switch must then        allow the voltage of the stage to exit from a zero voltage        unless the cell/cells placed in parallel keep their parallel        switch closed for another reason. If the voltage of the stage        does not succeed in varying after a certain time, then the        parallel switch is reactivated to prevent the parallel switches        of the cells placed in parallel from supporting the whole of the        current for too long. If on the other hand the voltage is no        longer zero (or close to 0), then the in-series cell switch is        activated;    -   if a cell has disconnected subsequent to too considerable a        charge (crossing above a voltage threshold), it may decide to        reactivate as soon as the voltage of the stage tends to be lower        than that of the cell (case where the parallel switch has not        been activated). If the parallel switch had been activated, then        the decision to deactivate it may be made on the basis of a        detection of a current in the parallel shunt circuit which is in        the direction of a discharging current. The opening of the        parallel switch is then followed by a closing of the cell        switch, a small lag between the opening of the parallel switch        and the activation of the series cell switch can be provided so        as to allow time for all the cells to detect the discharging        current;    -   if a cell has disconnected subsequent to too considerable a        current and if the parallel switch has not been activated, this        signifies that the cells placed in parallel have been able to        support the current and maintain the voltage, then the cell can        attempt to reconnect as soon as the voltage of the stage is        sufficiently close to the voltage of the cell;    -   if a cell has disconnected subsequent to too considerable a        current and if the parallel switch has been activated, it is        probable that the neighbour cells were either overly charged, or        overly discharged and no longer participated in the amassing of        the current. In this case, as soon as the current which flows in        the parallel switch goes below a threshold or becomes of        opposite sign to the current which caused the deactivation of        the cell (and supposedly the neighbour cells), then it is        opened. If a charging current is present, then the cell switch        is activated as soon as the voltage approaches the voltage of        the cell, and if the voltage does not succeed in rising after a        certain time, the parallel switch is reactivated (it is assumed        that a cell placed in parallel has not re-opened its parallel        switch and it cannot be allowed a considerable current for too        long). If a discharging current is present and if the voltage of        the stage begins to drop, then the series switch is closed (that        is to say as soon as it is certain that the parallel switch of        all the cells placed in parallel is open, otherwise it would not        have been possible for the voltage to fall), a small lag between        the opening of the parallel switch (and then the detection of        the voltage drop) and the activation of the cell switch can be        provided so as to allow time for all the cells to detect the        discharging current and then the voltage drop;    -   if a cell has disconnected subsequent to an irreparable failure        of the latter, then the cell switch is no longer ever        reactivated. On the other hand, the parallel switch which must        close in certain cases must be able also to open. If the        parallel switch has been activated subsequent to the detection        of the passage of the voltage of the stage through a value below        a threshold (a few −100 mV), then the latter can be re-opened        when the current passing through it is below a threshold or a        recharging current. If it has been activated subsequent to the        detection of the passage of the voltage of the stage through a        value greater than a threshold (maximum voltage that a cell can        attain on charge) then it can be re-opened when the current        passing it through is below a threshold or a discharging        current. In fact it is assumed that what has caused the        generalized closing of the parallel switches stems from the fact        that the cells placed in parallel have attained their full        charge or discharge or over-current and that if a contrary        current or one that is below a threshold appears in the        photovoltaic energy generation device, then the cells placed in        parallel will reactivate. If the neighbour cells placed in        parallel do not ever reconnect, then the voltage of the stage        will pick up again, either beyond the normal maximum voltage or        below the normal minimum voltage and again trigger the parallel        switches of the cells of the stage;    -   if a cell has disconnected subsequent to a reparable failure,        then the cell can be reconnected when the failure has        disappeared (for example when its temperature has gone back down        sufficiently or if the cell has been replaced). If the parallel        switch had been activated, then the same process as in the        previous point is followed.

The previous principles can be implemented in a similar manner on thebasis of centralized management.

All these operations of the method for managing a photovoltaic energygeneration device have been performed on the basis of an analysis by oneor more microcontroller(s). As a variant, as the actions to be performedare simple, it is possible to use all or part of an asynchronouselectronic circuit, without requiring a high-frequency clock to limitthe energy consumption of the solution. In such a variant, the detectionof a threshold would be done directly on an analogue measurement via acomparator and the action induced subsequent to a threshold crossingcould be executed in an asynchronous manner via logic circuits, usingfor example flip-flops, registers.

FIG. 22 illustrates a possible implementation according to such anapproach allowing the driving of a parallel transistor 34. In thisimplementation, measurement sensors, not represented, for measuring thevoltage of a module Vmod, the voltage across the terminals of a cellVcel, and the current I passing through a cell are used. These measuredvalues are compared with three threshold values, two values of high Vs1and low Vs2 thresholds for the voltage of the module, and a thresholdvalue Is1 for the current. Four operational amplifiers 90 (orcomparators) make it possible to compare these measured values with thethresholds explained, so as to determine, with the aid of several logicoperators 91 and delay cells 92, a final decision regarding the openingor otherwise of the module transistor 34. The delay cells 92 of thiscircuit can, in addition to their function of delaying the reaction to agiven event, ensure that the result of the comparison is stable over acertain duration, and take into account a transition only when thestability of the result of the comparison has been repeated over apredefined duration, so as to erase the scrambled measurements, forexample subsequent to noise caused by the switching of neighbour modulesor cells.

An advantage of this type of driving of a module transistor stems fromthe fact that there is no need to digitize the measured signals and thatthe reaction can be very fast, without however requiring veryhigh-frequency sampling of the signals. Moreover all the operations canbe done in parallel, this being very beneficial if it is desired thatall the cells be able to react in a synchronous manner, to exhibit anopening or a closing of a transistor on the basis of the voltage of thestage common to all the cells of the stage, and not on a clock edgewhich would not be common to each cell of the stage since the same clockcould not be shared without additional output on the cells. Such asynchronization can thus make it possible to reduce, or indeedeliminate, the risks of overlap between the closing of the celltransistors 23 and the parallel transistors 34.

Furthermore, the method for managing the photovoltaic energy generationdevice also implements an additional step of disconnecting all thepossible cells during a prolonged shutdown of use of the photovoltaicenergy generation device. This step affords considerable safetyespecially in the particular situations such as subsequent to anaccident or to a fire. When a considerable number of cells aredisconnected, and preferably all the cells, the risk of obtaining aconsiderable short-circuit between the cells, even in the case of aconsiderable incident, remains very low. Moreover, the isolation of thecells on shutdown prevents the cells from discharging through certaincells with the biggest leakage current or exhibiting defects.

According to an advantageous embodiment, the management method of theinvention comprises a control of switches of cells and/or of modules soas to obtain an output voltage of predefined value, and/or analternating output voltage according to a predefined setpoint.

Thus, the photovoltaic energy generation device management method alsoallows adaptation of the output voltage according to the desired use,for example to the need of an electrical load or of an electricalnetwork. This adaptation comprises for example the restricted choice ofa certain number of modules or of subsets to be used in series, theother modules remaining unused, when the total voltage required is lessthan the maximum voltage that can be delivered by the photovoltaicenergy generation device.

The adaptation of the output voltage of the photovoltaic energygeneration device of the invention can even take complex forms. Indeed,it is adapted for providing a sinusoidal output voltage, for example of220 V at 50 Hz to adapt to a public electrical network, or for asynchronous or asynchronous motor. FIG. 23 represents an exemplaryregulation of a photovoltaic energy generation device to obtain such avoltage output, implemented for example within the central computer 22of the embodiment of FIG. 14. This regulation relies on a block 80 forcomputing a setpoint value of the electrical parameters desired atoutput of the photovoltaic energy generation device, comprising thesetpoint voltage V_(cons) and the setpoint current I_(cons). As aremark, the setpoint can consist of a combination of these current andvoltage values, such as for example their product I_(cons)×V_(cons). Theblock 80 for determining at least one setpoint value can rely on avector control, taking into account the adjustment of the amplitude, ofthe frequency and optionally of the phase of the current/voltageparameter according to the type of motor to be supplied. Naturally, thisprinciple also operates with simpler situations, such as a need for a DCvoltage. Thereafter, the regulation block comprises a block 83 forcorrection, on the basis of the difference between the setpoint valuesI_(cons), V_(cons) and the corresponding actual values I_(actual),V_(actual), which transmits a need to a block 84 which determines thenumber of modules required in the photovoltaic energy generation deviceand optionally the particular cells of these modules to be used.According to a preferred embodiment, the choice of the cells to be usedin the modules is made at the level of the modules on the basis of thelocally measured parameters. Accordingly, this block 84 also receivesthe information regarding measurement of quantities performed at thelevel of the modules and cells of the photovoltaic energy generationdevice. Finally, a last block 85 implements the choice determined by theblock 84, and dispatches in particular the commands required for thevarious switches of the photovoltaic energy generation device. Thisresults at output in the actual values of the current I_(actual) and ofthe voltage V_(actual), which make it possible to attain the operatingvalues, such as a speed Spd and a torque Tor transmitted by the block82. Finally, a frequency-of-variation limiter and/or a low-passfiltering can act on the correction block 83, or on the return loop, toobtain an appropriate mean value, by limiting the cell switchingfrequencies, such as for example according to a frequency of 200 kHz foran output voltage of frequency 500 Hz.

This functionality for regulating the output voltage of the photovoltaicenergy generation device allows it to behave as a conversion structureof switched photovoltaic energy generation device type, which avoids theuse of a DC/DC converter at the output of the photovoltaic energygeneration device, to adjust the voltage to the needs of theapplication, and allows the use of the photovoltaic energy generationdevice according to the simplified layout of FIGS. 6 and 7, and nolonger like that of FIG. 1 of the prior art.

FIG. 24 represents an exemplary voltage wave which can be provided bythe photovoltaic energy generation device via a driving such asexplained hereinabove, for a voltage setpoint of sinusoid type at 50 Hz,of peak amplitude 40 V and centred on 40 V, and for a photovoltaicenergy generation device consisting of 20 modules of 4 volts each andwhose switching frequency is limited to 10 kHz (i.e. 100 switchings perperiod).

To be able to generate a single-phase voltage centred on 0, it isnecessary to be able to use either two columns and a differentialvoltage, or to add an H-bridge, such as illustrated in FIG. 25, whichmakes it possible to invert the voltage across the terminals of thephotovoltaic energy generation device on the basis of four switches 86,87, 88, 89, two 86, 87 at the level of a first terminal and two 88, 89at the level of a second terminal. When the two switches 86, 88 areclosed and the other two open, the output voltage V_(out) is positive.On the contrary, when the two switches 87, 89 are closed and the othertwo open, the output voltage V_(out) is negative.

FIG. 26 illustrates a more detailed implementation of the principledescribed in FIG. 25, on the basis of a photovoltaic energy generationdevice structure such as presented in FIG. 14, comprising by way ofexample five modules of two cells. For each cell 11, a cell transistor23 is provided, in series with the cell, and a module transistor 24, inparallel, is provided for each module 12, as explained previously.Moreover, at least one sensor for measuring a quantity characteristic ofa cell is present at the level of the module, not represented for thesake of simplification. A local control circuit 27, at the level of themodule 12, drives the transistors 23, 24 through control signals 41, ashas been explained previously, under the orders of a central computer 22through the communication bus 21 and by way of an interface 37 forming agalvanic isolation. The photovoltaic energy generation device moreovercomprises four switches 86, 87, 88, 89 such as presented hereinabove,which are transistors according to this embodiment, driven respectivelyby the control circuits 27 of the upper and lower extreme modules of thephotovoltaic energy generation device, through control links 90.

As a remark, the method for managing the photovoltaic energy generationdevice implements an optimal switching of the switches 86, 87, 88, 89.For example, if the output voltage must be a sinusoidal voltage, theswitching of the transistors is performed when the voltage passesthrough 0, so as to limit the switching losses. If a 50-Hz wave isdesired at the output of the photovoltaic energy generation device, itis necessary to undertake 50 closings/openings per second of thetransistors of the H-bridge.

Moreover, the method for managing the photovoltaic energy generationdevice also advantageously implements intelligent management of thetransistors of the H-bridge similar to the steps envisaged for themanagement of the series transistors or module transistors. For example,it is also possible to associate with them a measurement of temperatureor of voltage and/or current, and to take a decision to open atransistor if the measured quantity exceeds a certain threshold, forexample in the case of overly high temperature. This measured quantitycan naturally be transmitted to a local and/or remote processing circuitso as to implement this intelligent management.

The two extreme modules, upper and lower, of the photovoltaic energygeneration device incorporate more numerous electronic components thanthe other modules. All these components are advantageously suppliedelectrically by the voltage available at the level of the module. Inthis case, the extreme modules are invoked more than the others.

Ultimately, the solution described previously exhibits numerousadvantages, among which:

-   -   it relies on a multitude of elementary switches, that is to say        a multitude of transistors according to the preferred        embodiment, spaced far apart, thereby making it possible easily        to evacuate the energy dissipated by their operation, since this        dissipated energy takes the form of a multitude of small amounts        of energy that are scattered within the structure of the        photovoltaic energy generation device;    -   it makes it possible to perform real-time optimization of the        operation of the cells of the photovoltaic energy generation        device via dynamic steering;    -   it makes it possible to disconnect failed cells;    -   it makes it possible to adjust the output voltage of the        photovoltaic energy generation device in a gentle manner        (low-frequency switching <1000 Hz and with fairly low voltage        settings, for example 4V), without requiring high-frequency        chopping of the full voltage of the photovoltaic energy        generation device. It makes it possible to adjust a DC voltage        desired for the driving of DC motors or for a link with an        electrical distribution network.    -   it makes it possible to individually isolate a cell of a module,        by making it possible in particular to measure its no-load        voltage even if the photovoltaic energy generation device is in        operation;    -   it makes it possible to isolate all the cells, for example        subsequent to the detection of a major failure, making it        possible to dismiss all electrical risks in respect of the user        or people who will have to intervene, for example firemen in        case of fire.

By measuring at one and the same time the voltage of the cells and thevoltage of a module of the photovoltaic energy generation device, it ispossible to deduce therefrom the voltages across the terminals of thepower transistors. On the basis of these voltages and of the currentpassing through the cells or transistors of modules, it is possible, incertain configurations, to detect whether a transistor has failed. Thus,the photovoltaic energy generation device also implements a method fordiagnosing the operation of all or some of the transistors which fulfilthe essential functions of switches, which can comprise all or some ofthe following steps:

-   -   if upon the opening of the transistors of cells, the voltage of        the stage remains substantially equal to that of the cells while        a current flows, this implies that at least one of the cell        transistors no longer opens. To ascertain which, it suffices to        investigate through which cell the current flows. Thus, the        diagnosis method comprises a control step commanding the opening        of all the transistors of cells of a module, the measurement of        the voltage of the module, and in the case of a value close to        the voltage of a cell, measurement of the current passing        through each cell and classification of cell transistors as        “failed” if a current flows therein. Hereinafter, the module        transistor(s) associated with a module of which at least one of        the cell transistors has failed (remains closed) is(are) no        longer activated so as not to create any short-circuits. The        method can comprise a complementary step of transmitting the        data relating to the identity of the failed switches and/or of        the maximum current that can be delivered by each module to a        local and/or central unit. A user must be able to know which        transistors have to be changed;    -   if upon a command for opening the parallel transistors, the        voltage of the stage remains substantially zero while a current        flows, then at least one parallel transistor has not opened and        has failed. The measurement of the current through each parallel        transistor of the module (case for example of a transistor in        parallel with each cell) makes it possible to determine the        failed parallel transistor or transistors. The diagnosis method        therefore comprises a control step for commanding the opening of        the parallel transistors, for measuring the voltage and the        current, for identifying the failed module transistors if the        voltage is zero while a current flows. Hereinafter, the cell        transistors associated with a module whose parallel transistor        has failed (remains closed) are no longer activated so as not to        create any short-circuits. The module concerned is no longer        used until its module transistor or the parallel switches is or        are replaced;    -   if upon the command for closing a cell transistor, a voltage        drop appears on a transistor while the current in the associated        cell is substantially zero, then the cell transistor has failed        and no longer closes. Such a situation limits the current that        can be provided by a module. The central computer of the        photovoltaic energy generation device is informed by indicating        to it the maximum current that the module can still support.        Moreover, the user is warned of the transistor to be changed;    -   similarly, if the command for closing a module transistor gives        rise to a voltage drop on the transistor while the current        therein is zero, then this signifies that the transistor has        failed and no longer closes. This limits the current that the        module can pass when the cells are disconnected. The central        computer is warned by indicating to it the maximum current that        the module can still support. Moreover, the user is warned of        the transistor to be changed;    -   when a current in a branch is of opposite sign to the current        flowing in the other branches, beyond a certain threshold, then        there is diagnosed a leakage current of the normally open        transistor of this branch. The central computer is warned by        indicating to it the value of the leakage current and the        maximum current that the module will still be able to support in        the case of a partial or complete failure of the transistor in        the passing state which could arise thereafter, according for        example to model-based anticipation of the future degradation of        the transistor. The main computer will be able for example to        favour maintaining the module in a particular state (activation        of the cells or of the parallel transistor(s)) so as rather to        maintain the transistor with leakage current in a closed state        in order to avoid losses, its heating, and to limit its        switchings so as to limit its degradation. Moreover, the user is        warned of the transistor to be changed.

Naturally, the invention is not limited to the previous examples. Inparticular, several measurement sensors per cell have been implementedbut as a variant other numbers of measurement sensors can be chosen orno sensor. Moreover, it is possible to use other types of measurementsensors than those described, to measure quantities characteristic ofthe state of a cell other than the voltage, the current or thetemperature.

Moreover, the previous embodiments have been described by implementing acell switch for each cell of the photovoltaic energy generation device.However, it would be possible to obtain an improvement of a photovoltaicenergy generation device by managing only part of its cells according tothe concept of the invention, and therefore employing the cell switcheson only part of the cells of the photovoltaic energy generation device,therefore at least one switch, advantageously on at least two cells ofone and the same module so as to allow a certain flexibility in thismanagement. Certain modules might not implement the previously describedapproach and it is possible to contemplate a photovoltaic energygeneration device associating conventional parts and improved modulesaccording to the invention. Moreover, a module switch has been describedfor each module of the photovoltaic energy generation device, or as avariant of the parallel switches associated with each cell. Suchswitches remain optional and could be eliminated, in a simplifiedversion of the invention. Moreover, the invention covers all theintermediate embodiments incorporating one or more module switch(s)and/or parallel switches, for part only of the modules.

Finally, the examples represented comprise few cells for the sake of theclarity of the figures. However, the embodiments envisaged are adaptedfor the implementation of energy generation devices able to provide aconsiderable output voltage, that may attain several hundred volts, forexample for a 220-volt mains connection. They are therefore adapted fordevices comprising a considerable number of modules, in particulargreater than or equal to 8.

FIGS. 28 to 30 illustrate for this purpose variant embodiments forimplementing a shunt function for several modules of a photovoltaicenergy generation device, which rely on complementary switches disposedin parallel with several modules making it possible to add a circulationpath of the current when several modules are deactivated, thus limitingthe losses.

Thus, FIG. 28 adds a first series of switches 214 each making itpossible to shunt four consecutive modules, a second series of switches314 each making it possible to shunt six consecutive modules, a thirdseries of switches 414 each making it possible to also shunt sixconsecutive modules but staggered with respect to the second series, afourth series of switches 514 each making it possible to also shunt sixconsecutive modules but staggered with respect to the previous twoseries, a fifth series of switches 614 each making it possible to shunteight consecutive modules and a sixth series of switches 714 each makingit possible to also shunt eight consecutive modules but staggered withrespect to the fifth series.

All the switches of these various series are disposed between the lowerand upper terminals of different modules, in parallel with one another.Naturally, their management is coherent to avoid creating short-circuitsituations, as has been explained in the previous examples.

The two FIGS. 29 and 30 illustrate two other variant embodimentsaccording to the same approach.

The advantage of these various embodiments is to add circulation pathsof the current which are much more direct upon the deactivation ofseveral modules by virtue of switches which shunt several stages at oneand the same time, thereby generating much fewer losses. Thus, at eachinstant, according to the number of modules required, a substantiallyoptimal configuration is implemented to minimize the total resistance ofthe photovoltaic energy generation device.

The various switches mentioned, cell and/or module and/or parallelswitches, have been implemented with the aid of transistors. NMOS orPMOS transistors have been represented mainly, but it is howeverpossible to use NPN and PNP bipolar transistors, which exhibit theadvantage of being able to be controlled with a fairly low voltage, FET,JFET, IGBT, GaN transistors, relays, etc. As a variant, any other typeof switches than those described could be implemented, such asthyristors if the current is naturally required to reverse at the momentwhere it is desired to open it.

The photovoltaic energy generation device of the invention can bemanaged by an intelligent unit, a computer or local and/or remoteprocessing circuit accessible through a local communication device, thiscomputer being able to comprise any software element and/or hardwareelement to manage the photovoltaic energy generation device, inparticular to determine the configuration of its switches. Accordingly,the photovoltaic energy generation device can incorporate any actuationmeans, any control circuit, for its switches.

Numerous other variant embodiments of the invention can be easilycontemplated through a simple combination of the previously describedembodiments and/or their variants.

As a remark, the communication within the photovoltaic energy generationdevice and/or to an outside unit can be done according to a carriercurrent principle, provided that the current demanded by a load is nottoo considerable to authorize the disconnection of certain cells.Indeed, this principle relies on an intentional alternation ofconnections and disconnections of certain cells of the photovoltaicenergy generation device, so as to create a modulation of inducedcurrent and a modulation of power at the level of a module, whichpropagates to the whole of the photovoltaic energy generation device andbeyond. This power modulation is therefore visible by the other modulesof the photovoltaic energy generation device and by an outside load,thereby making it possible to use it to transmit information accordingto any communication protocol, existing and standardized or not. Amaster circuit may for example be defined which interrogates all thecells in turn, through their address, each cell thereafter responding ina dedicated time slot. The master can for example request an item ofinformation such as a measurement of voltage, current and/or temperatureat a certain cell, and then the latter can dispatch the item ofinformation requested with optionally a code making it possible toinform regarding a possible failure or otherwise. This principle thusallows various cells of the photovoltaic energy generation device tocommunicate simply with one another, or to communicate towards a centralcomputer or a processing circuit of the photovoltaic energy generationdevice or towards an outside unit. As a remark, the modulation ofcurrent can be done without disconnecting a cell completely, but simplyby modulating the resistance in the passing state of the celltransistor, that is to say by modulating the gate voltage of thetransistor around a bias point. This modulation of resistance in thepassing state can also be done on the module transistor when the latteris activated. This then makes it possible to communicate even if thestage is deactivated by the opening of the cell transistors.Communication by carrier current makes it possible to modulate aconsiderable current at the level of a module without howeverengendering considerable electrical losses. Indeed, this currentmodulation is done by modulating a consumption of current which issimply stored and destored since it belongs to a photovoltaic energygeneration device coupled to a storage element, this implying that thelosses which exist in a dissipative element such as a resistor or atransistor in linear mode, conventionally used for a carrier currentsystem, do not exist.

FIG. 27 thus schematically illustrates the basic implementation, whereina first module 12 of a photovoltaic energy generation device generates acommunication signal 100 by the actuation of at least one cell switch13, while a corresponding signal 101 is thereafter received at the levelof a second module 12′ of the photovoltaic energy generation device.

FIG. 31 illustrates a variant of the embodiment of the invention, inwhich the photovoltaic energy generation device is separated into fourequivalent parts or subsets comprising several modules of several cells.The structure of these modules incorporates the concept such asdescribed above, and here each cell comprises a cell switch and eachmodule a module switch. These various parts can be either disposed inseries, by closing first switches 103 linking them and by opening secondswitches 104, this then representing a geometry such as describedpreviously with reference to FIG. 7, or in parallel by opening on thecontrary the first switches 103 and by closing the second switches 104.As a variant, any intermediate combination is possible, such as thegrouping of the parts two by two in series, and then the disposition ofthese groupings of two parts in parallel. This variant makes it possibleto have the choice between a considerable output voltage Vs or a lowervoltage but a greater output current Is than that which would beobtained with all the parts in series. Thus, this structure becomesutilizable as soon as the desired output voltage is lower than thatwhich can be provided by half the modules. If this voltage is lower thana quarter of that which can be provided by the entirety of the modulesin series, then the four parts represented can be used in parallel.

As a variant, the same approach could be implemented with any othernumber of parts; each module could even represent a part, adapted for anassociation in series or in parallel with the remainder of thephotovoltaic energy generation device. Moreover, these various partscould be mutually different, not comprise the same number of cells. Themethod for managing the photovoltaic energy generation device could thuscomprise a step of automatic computation of the number of parts to beplaced in parallel, according to a predetermined period, as a functionof the voltage and current demanded at output, and then a step ofactuating the switches 103, 104 so as to obtain the photovoltaic energygeneration device geometry best adapted to the need, at each instant.

FIG. 32 thus illustrates an implementation of the principle describedhereinabove with reference to FIG. 31. In this example, the photovoltaicenergy generation device comprises only two parts of three modules toobtain clarity of the representation. Naturally, this principle can beduplicated for a photovoltaic energy generation device of a hundred orso modules, which is divisible into a multitude of parts. Thephotovoltaic energy generation device represented corresponds to thatdescribed with reference to FIG. 14. All the modules comprise theelectronic components already described in detail and are linked to acentral computer 22 by a communication bus 21 and a galvanic isolation37. The photovoltaic energy generation device is moreover equipped withan H-bridge by way of four switches 86 to 89 such as explainedpreviously. Finally, the splitting of the photovoltaic energy generationdevice into two parts is obtained by the addition of three transistorsforming the switches 103, 104, 104′ explained previously. As isillustrated, two transistors 103, 104 are positioned in the central partof the photovoltaic energy generation device so as to be driven bycontrol circuits 27 for the adjacent modules distributed physically oneither side of these transistors. Furthermore, a transistor 104′ ispositioned towards the lower end of the photovoltaic energy generationdevice and is driven by a signal 90 of the control circuit for the lowermodule of the photovoltaic energy generation device. Naturally, theseswitches 103, 104, 104′ could be distributed differently within thestructure of the photovoltaic energy generation device.

FIG. 33 schematically illustrates the various blocks of the computer 22which implements a method for managing the photovoltaic energygeneration device, which comprises several modules 12 which can beplaced mutually in series or in parallel, according to the principledescribed hereinabove, and which is linked to the mains 5. This computerimplements a first computation in a block 82 of the ratio of the voltageof the mains 5 to the mean voltage of a module or stage 12, obtained ina first block 81, thereby giving the number, non-integer, of modules tobe placed in series to attain, under no load, the voltage correspondingto that of the mains 5. It deduces therefrom in a block 83 the number Nof modules to be placed in series to obtain, with the desired current,the voltage corresponding to that of the mains 5. Accordingly, arounding block is disposed at the output of this block 83, making itpossible to obtain an integer number. A block 84 computes a meandeviation between the voltage of the modules and their optimal voltage,and implements feedback to approach the optimal situation, by blocks 85.This solution amounts to modifying the output current so as to approacha situation more favourable for attaining optimal operation at the levelof each module. Accordingly, a coefficient α is chosen, preferablybounded, to adjust the overall current so as to attain optimal operationof the module. The result is also transmitted to the block 83 forcomputing the required number of modules. Thereafter, a block 86performs the selection of the N particular modules to be used, inparticular by taking account of the deviation between their voltage andtheir optimal voltage, favouring those whose voltage is the furthestabove this optimal voltage.

FIG. 34 thus illustrates another exemplary embodiment of a photovoltaicenergy generation device comprising eight modules of two cells, saidmodules being distributed in two parts of four modules, each partrespectively retrieving a voltage V₁ and V₂. This photovoltaic energygeneration device moreover comprises ten MOS transistors, of which fivetransistors K11 to K15 are tied to the first part and five transistorsK21 to K25 are tied to the second part. These ten transistors arecontrolled directly by the adjacent modules. They make it possible toimplement the two functions of voltage inversion and of placing the twoparts of the photovoltaic energy generation device in series orparallel. Accordingly, this does indeed entail a solution equivalent tothe previous layout. The total voltage V_(s) retrieved by thephotovoltaic energy generation device is in fact defined by thefollowing formulae:

V _(s) =V ₁ +V ₂ when the transistors K13, K14 and K21 are closed, theothers being open,

V _(s) =−V ₁ −V ₂ when the transistors K11, K23 and K24 are closed, theothers being open,

V _(s) =V ₁ =V ₂ when the transistors K12, K22, K15, K25, K14 and K21are closed, the others being open,

V _(s)=−(V ₁ =V ₂) when the transistors K12, K22, K15, K25, K11 and K24are closed, the others being open.

This embodiment comprises transistors K14, K15, K24 and K25 which arenever subjected to a voltage greater than V₁ or V₂, thereby making itpossible to choose low-voltage transistors, able to receive a highercurrent without generating too many losses. The ten transistors arecontrolled via electronics which can be powered and placed on the lowerand upper modules of the two parts of the photovoltaic energy generationdevice, as in the previous cases. As the source potentials of thesetransistors are referenced with respect to these modules, thissimplifies their control.

In the case of a photovoltaic energy generation device comprising Nmodules, if the computation determines that n modules in series arenecessary to obtain a required voltage, then the following computationcan be performed:

If n<N/2 then placing of two parts in parallel, by splitting thephotovoltaic energy generation device into two;

if n<N/3, division of the photovoltaic energy generation device intothree parts, etc.

As a variant, a regulation of hysteresis type can be chosen, to avoidswitching the switches too often when the required voltage varies arounda limit value like N/2. Accordingly, it may be decided to undertake thedivision of the photovoltaic energy generation device into p parts whenn<N/p−q, where q is an integer constant.

As a variant, the method for managing the photovoltaic energy generationdevice can implement any regulation around an output voltage and/orcurrent value. When the output voltage is less than the setpoint value,the number n of modules in series is increased, and on the contrary ifit is greater than the setpoint value, then this number n is decreased.To prevent the number n from oscillating between two values to attain asetpoint value which is unattainable with an integer value of n, afrequency-of-variation limiter can be used and/or a low-pass filteringat the level of the corrector or of the return loop so as to attainregulation on a mean value.

If the photovoltaic energy generation device must provide an alternatingvoltage, or any voltage varying over time according to a given period,the placing in parallel of various parts of the photovoltaic energygeneration device can be decided on similar criteria, applied to theamplitude of the sinusoid or of the variable voltage to be provided, soas to avoid toggling from one mode to another too often, at each period.Globally, the required current may be all the higher, the lower theamplitude of the required voltage.

FIG. 35 represents an embodiment of a control circuit for commanding thetransistors 23, 24, via the discharging of an inductance 105, previouslycharged through the closing of two transistors, PMOS 106 and NMOS 107,by which it is flanked. When the inductance 105 is sufficiently charged,the NMOS transistor 107 opens while the PMOS transistor 106 remainsclosed. The current then passes through the diode 108 and will thencharge the gate of the module transistor 24, sufficiently to induce itschange of state.

Moreover, the invention is also compatible with a three-phaseimplementation. FIG. 36 illustrates in a simple manner a photovoltaicenergy generation device comprising three columns 109, each of similararchitecture to a photovoltaic energy generation device according to theinvention such as described above, making it possible to supply athree-phase motor 15.

FIG. 37 illustrates a variant embodiment of a photovoltaic energygeneration device adapted for delivering a three-phase voltage to athree-phase motor 15, which differs from the previous embodiment throughthe fact that each column 109 of the photovoltaic energy generationdevice is equipped with switches 86 to 89, advantageously transistors,to produce H-bridges such as explained in conjunction with FIG. 25. ThisH-bridge makes it possible to double the peak-to-peak control voltagefor the motor and therefore to halve the output current for one and thesame output power (Ueff*Ieff=cst). These switches switch twice perperiod, that is to say on each change of sign of the output voltage.This architecture, with respect to that of FIG. 36, makes it possible toprevent the current provided by a column from moving in the form of areverse current in another column at certain moments of the period. Inthis solution, the three coils of the three-phase motor 15 can besupplied independently. This isolation can make it possible togalvanically isolate each of the columns 109 of the photovoltaic energygeneration device. This isolation may in particular be useful if thethree columns 109 are separated into three photovoltaic energygeneration device blocks which are physically distributed in variouslocations, for example within a vehicle for reasons of electricalsafety.

FIG. 38 illustrates another variant embodiment making it possible toprovide a three-phase power supply. The device used comprises thearrangement in series of two structures or two photovoltaic energygeneration device columns such as are described in relation to FIG. 25.As has been presented, each column is adapted for retrieving analternating output voltage of sinusoidal type. By applying a phase shiftof 2π/3 to the voltages retrieved by these two columns, it is possibleto recover a three-phase voltage as output of the photovoltaic energygeneration device. As a remark, each column is linked to its centralcomputer 22, 22′ by respectively a communication bus 21, 21′ and thesetwo computers 22, 22′ are linked up with a main computer 222 whichmanages the photovoltaic energy generation device as a whole and inparticular the coordination of its two columns.

The three computers thus share the implementation of the method formanaging such a photovoltaic energy generation device. By way ofexample, the main computer 222 determines the number of stage n1 and n2to be used on respectively each of the two columns of the photovoltaicenergy generation device. Accordingly, a solution consists in choosingthe numbers n1 and n2 according to the following rule:

n1=rounded to the integer nearest to [(amplitude of the setpoint peakvoltage/voltage of a module)*sin(2πft)]

n2=rounded to the integer nearest to [(amplitude of the setpoint peakvoltage/voltage of a module)*sin(2πft)]

The computer defines a desired output setpoint, including the frequencyf of the signal and its amplitude. In the case of the use of thephotovoltaic energy generation device to supply a motor, the outputvoltage and the current and the speed of the motor can be managedaccording to a servocontrol loop. The numbers n1 and n2 are adjusted atany instant t to attain the setpoint defined by this servocontrol.

As a supplement, the two computers 22, 22′ dedicated to each column ofthe photovoltaic energy generation device determine more precisely themodules (and optionally the cells) to be used in order to comply withthe numbers n1 and n2 defined while attaining the required values ofvoltage and current. This choice is carried out in such a way as tocomply with the state of the various modules. Accordingly, each computer22, 22′ receives the item of information regarding the state of eachmodule of its column, thereby making it possible to determine preciselywhich n1 and n2 modules are used at each instant. Thus, the cells whichmake it possible to obtain the short-term required current are selected,and remain connected until the crossing of the current peak, therebyavoiding overly numerous connections and disconnections of the modules.The modules which are able to provide only a lower current are then usedonly when the required peak current is less than the capacity in termsof current of these modules.

Moreover, the main computer 222 also transmits the item of informationregarding the sign of the required voltage, so that each columnpositions its H-bridge as a function. According to an advantageousembodiment, this item of information is transmitted to each column bymodifying the sign of the numbers n1 and n2.

Moreover, the management method also comprises a step of transmission tothe main computer 222 of the item of information regarding the state ofeach module of the two columns. It is thus possible to compute themaximum current and the voltage that can be provided by the photovoltaicenergy generation device to take account thereof during the managementof the photovoltaic energy generation device: in case of need, the maincomputer 222 can thus implement a limitation of the peak currentrequired or absorbed, or indeed a limitation of the speed of the motorin the case of a power supply of the motor.

Ultimately, all the embodiments of previously illustrated energygeneration devices show that it is possible to use various types ofswitches to fulfil different and complementary functions, among which:

-   -   cell switches, to connect or disconnect a particular cell of the        device;    -   parallel switches, to by-pass or otherwise a particular cell of        the device;    -   module switches, to by-pass or otherwise a module of the device;    -   switches to by-pass or otherwise several modules simultaneously        of the device;    -   switches to invert or otherwise the voltage at the output of the        device;    -   switches for series/parallel inversion to dispose certain        sub-parts of the device in series or in parallel.

According to an advantageous embodiment, as has been described, allthese switches are driven by a control circuit powered by at least onecell of the device itself, that is to say powered locally, withoutrecourse to an outside power supply. Moreover, the driving of a switchis preferably carried out by a sufficiently close control circuit,powered by at least one cell of the module which is closest or inproximity, so as to bring into play voltages of one and the same orderof magnitude between the control circuit and the driven switch, forexample the driven transistor. Accordingly, it is advantageously chosento drive a switch, one of whose terminals, source or drain terminal inthe case of an NMOS transistor for example, is linked to a voltage of acertain module by a control circuit powered by this same module or anadjacent module, more exactly by at least one cell of one of thesemodules. More generally, it will be possible to choose any controlcircuit whose power supply link is on a module whose potentialdifference with the terminals of the switch does not exceed a predefinedthreshold, which would run the risk of damaging the switch, of creatinga situation of electrical risk. This threshold is defined by safetystandards and depends on the type of switch employed. This local powersupply, in proximity, exhibits the second advantage of allowing the useof drive links of short length between the control circuit and theswitch.

Thereafter, it should be noted that the control circuit must allow thereliable actuation of the various switches. In a case where the variousmodules exhibit a potential difference of 3 V or less and the switch isof NMOS type, a control circuit preferably incorporates a voltagebooster (for example a charge pump) to increase the voltage present onits input terminals, and use as output a higher voltage for theactuation of the switches, as a function of these latter. In the case ofan NMOS transistor for example, it will be chosen to power its gate witha voltage such that the voltage difference between its gate and itssource is of the order of 20 V, to guarantee reliable actuation.

FIG. 39 thus illustrates an exemplary use of such a photovoltaic energygeneration device applied to a resistive load, with certain assumptionsregarding aging and loss of capacity of certain modules.

The invention has been described with embodiments in which each stage ormodule is composed of cells, associated with switches driven by acontrol circuit. However, it is possible to contemplate variants inwhich not all the cells comprise a cell switch, and/or in which not allthe modules are driven, as has been mentioned previously.

Moreover, it has been seen that it is beneficial to be able to modifythe number of cells in series or in parallel, so as to more easily adaptto the need as a function of sunshine. FIGS. 40 to 46 illustrate forthis purpose other embodiments of photovoltaic energy generationdevices, wherein the cells are organized differently inside the modules,so as to facilitate the modification of their number in series orparallel and adapt to the conditions of sunshine and demand of a load.

Thus, FIG. 40 schematically represents an embodiment of the inventionwherein a photovoltaic energy generation device comprises a multitude ofcells 111 organized as several modules 112.

In this embodiment, each module 112 comprises a lower terminal 117,linked to a lower neighbour module, and an upper terminal 118 for aseries link with the upper neighbour module. Each module is composed ofbricks 120 disposed in parallel between its two terminals 117, 118. Inthis embodiment, each brick 120 comprises two vertical branchesextending between its two terminals, lower 117 and upper 118, on whichare respectively disposed in the following order from bottom to top: acell 111 and a switch K1 on the first branch, and a switch K3 and a cell111 on the second branch. Moreover, a transverse branch comprising athird switch K5 links the two intermediate terminals 116 disposed oneach of the two vertical branches between the cell 111 and the switchK1, K3.

This architecture allows a brick 120 to occupy the following variousconfigurations:

-   -   if the switches K1 and K3 are closed and the switch K5 is open,        then the two cells 111 of the brick are disposed in parallel:        this configuration makes it possible to obtain the maximum        current through the brick;    -   if the switches K1 and K3 are open and K5 closed, then the two        cells 111 of the brick are disposed in series: this        configuration makes it possible to obtain the maximum voltage of        the brick, and the maximum voltage of a module 112;    -   if the switch K5 is open and a single of the two switches K1 or        K3 is closed, then a single of the two cells of the brick is        active;    -   finally, if all the switches are open, the two cells of the        brick are disconnected from the remainder of the device.

It is thus apparent that this architecture allows each brick andtherefore each module to provide a zero, simple or double voltage, azero, simple or double available current, simply by choosing theposition of the three switches K1, K3, K5 disposed at the level of thecells of a brick. For this reason, these three switches will simply becalled “cell switch 113” subsequently.

On the chosen embodiment, each module 112 also comprises a switch K6 114in parallel with the bricks 120 of the module 112, thus making itpossible to short-circuit the whole of the module: accordingly, we shallcall it a “module switch 114” subsequently. It is useful when all thebricks of a module are in the disconnected configuration. As a remark,in this embodiment, the closing of the switch K6 requires that theswitches K1 and K3 be reversible in voltage.

The use of such a photovoltaic energy generation device to supply aload, such as a motor, makes it possible to circumvent the intermediateconverters used in the prior art, as has been explained previously.

FIG. 41 represents a variant embodiment in which each brick 120comprises two additional switches K2, K4, disposed on each verticalbranch on the cell 111 side with respect to the intermediate terminal116. Such an architecture offers additional configurations, further tothe configurations already explained in relation to the previousembodiment. It makes it possible in particular to impose a zero voltagedifference between the two terminals 117, 118 of a module, by closingthe three switches K1, K3, K5 and by opening the other two switches K2,K4.

FIG. 42 illustrates another embodiment in which the bricks presented inthe previous embodiments are associated two by two in each module 112 soas to allow cells to be placed in series or in parallel four by four,rather than two by two. Indeed, two bricks 120, 120′ are linked by threebranches and three additional switches K7, K8, K9 disposed respectivelybetween the two lower terminals of the two bricks, between their twoupper terminals, and between the upper terminal of the first lower brick120 and the lower terminal of the second upper brick 120′.

The three so-called “intermediate” additional switches K7, K8, K9between the two bricks 120, 120′ can occupy the followingconfigurations:

-   -   K7 and K8 closed, K9 open: the two bricks 120, 120′ are disposed        in parallel between the two terminals 117, 118 of the module;    -   K7, K8 open, K9 closed: the two bricks 120, 120′ are disposed in        series between the two terminals 117, 118 of the module.

As the cells 111 of each brick 120, 120′ can themselves be situated inseries or in parallel, it is apparent that the following configurationsare possible:

-   -   the four cells 111 can be situated in parallel between the        terminals 117, 118 of the module;    -   the four cells 111 can be situated in series between the        terminals 117, 118 of the module;    -   two sets of two cells in parallel can be situated in series;    -   two sets of two cells in series can be situated in parallel.

As a remark, four switches K10, K11, K12 and K13 are disposed on theoutput of the module. They make it possible to cancel the output voltageof the module (between the potentials of the connections situatedbetween K10 and K11 and between K12 and K13) without requiringbidirectional transistors at the level of K1, K3, K1′ and K3′, byclosing K10 and K12 (K11 and K13 open) or by closing K11 and K13 (K10and K12 open). These four transistors moreover make it possibleoptionally to invert the output voltage of the module. As the maximumvoltage of the module is relatively limited (for example less than 30V), this makes it possible to use transistors of low voltage withstand,which are less expensive and less resistive than transistors which oughtto withstand the full voltage of the device so as to effect a voltageinversion only at the level of the device. Each of these modulesequipped with their output inverter are thereafter placed in seriesand/or parallel to attain the peak voltages/currents desired at thelevel of the device.

FIG. 43 represents a variant of the previous embodiment, in which eachbrick comprises five cell switches 113 K1, K2, K3, K4, K5, in a mannersimilar to the embodiment illustrated in FIG. 41. Moreover, the modulesare simply disposed in series, without the switches K10 to K13 providedin the previous embodiment.

FIG. 44 shows in a schematic manner the architecture provided for at thelevel of a module for the management of such a photovoltaic energygeneration device. This same management architecture can readily beimplemented on all the other embodiments of photovoltaic energygeneration device.

One or more measurement sensors, not represented, for measuring forexample the temperature, the voltage and/or the current, are providedfor each cell of the module 112 and communicate their measurements to ameasurement unit 135. The measurements performed by this or thesesensors are transmitted to a local processing circuit 130, via amultiplexer for example, by communication pathways, not represented. Theprocessing circuit 130 thus receives these data through a communicationpathway 131 performing a digitization, of “ADC input” type; or as avariant, these signals arrive already digitized, this digitization beingcarried out at the level of the multiplexer. According to a possibleembodiment, the processing circuit 130 can be a microcontroller having asufficient number of input/output to interrogate all of the sensors. Allthe transistors used to form the cell switches 113, to form the devicefor series/parallel inversion between the bricks of the module (K7, K8,K9), and to form the device for series/parallel inversion with theadjacent modules (K10 to K13), are driven by a control circuit 127 whichtransmits control signals 141 to them, under the orders of theprocessing circuit 130. Finally, the latter is linked to the centralcomputer by the communication bus 121 and by way of an interface 137forming a galvanic isolation. All these components associated with asingle module are powered by the voltage of at least one of the cells111 of the module 112, according to the solutions explained during theprevious embodiments, for example by way of a link 128 and of a diode140. As in the case of FIG. 42, it is possible to contemplate a variantembodiment without the transistors K2, K4, K2′ and K4′ represented inFIG. 43.

FIG. 45 illustrates another embodiment of a photovoltaic energygeneration device of which a module comprises the association of fourbricks 120 such as presented previously, to form a basic structure offour bricks that we will call a “superbrick” 156. This superbrickcomprises a first brick linked to the lower terminal 117 of the module,and linked to a second brick linked to the upper terminal 118 of themodule by way of three switches K12, K13, K14 making it possible todispose these two bricks in series or in parallel, according to a mannerof operation explained previously. This same association of two bricksis disposed between the two terminals, lower 117 and upper 118, of themodule in parallel with the two bricks described previously. These fourbricks together form a superbrick, which serves as the basis for thearchitecture of the photovoltaic energy generation device. The lattertherefore comprises a multitude of other superbricks, not represented,disposed on the same module in parallel with the superbrick illustratedand/or on the other modules. This superbrick offers a multitude ofpossibilities for arranging eight cells, either all in parallel, or intwo parallel vertical branches each of four cells in series, oraccording to intermediate configurations such as four vertical brancheseach of two cells in series for example.

FIG. 46 presents a variant of the previous embodiment in which twointermediate terminals 116, 116′ of the two lower bricks of thesuperbrick are linked, as are the two upper terminals of these same twobricks. This configuration offers the additional possibility of placinga cell of one of the two lower bricks in series with a cell of the otherbrick for example.

As a variant, other links between the four bricks of the superbrick canbe implemented, such as a link between intermediate terminals of the twoupper bricks, in a manner similar to the layout chosen for the two lowerbricks, and/or a link between the other intermediate terminals of thetwo lower bricks, etc.

Naturally, these embodiments described with reference to FIGS. 40 to 46can be managed by the photovoltaic energy generation method describedpreviously. Moreover, the devices illustrated can be combined togetherto propose other variant embodiments.

In a fractal manner, it is possible to associate as many bricks asdesired to ensure series or parallel placements of a desired number ofcells. For example, returning to the example of FIG. 42, it is possibleto place the two subsets of two elementary bricks in series or parallelvia the transistors K7, K8 and K9. It is possible to extend thisprinciple, each time rising one level by associating two groups of fourelementary bricks via transistors K7′, K8′ and K9′ and then K7″, K8″ andK9″, etc., to form a module containing a more considerable number ofcompletely switchable series/parallel cells and making it possible togenerate an output voltage varying in increments of an elementary cellvoltage (from the voltage of an elementary cell to the voltagecorresponding to the whole set of cells in series). If moreover avoltage inverter is placed at output, the module can take an outputvoltage ranging from more or less the voltage of all the cells inseries, by cell voltage increments.

1. Photovoltaic energy generation device comprising several cells,comprising a photovoltaic cell, comprising one or more elementaryphotovoltaic cell(s), and a storage element connected to the terminalsof the photovoltaic cell, wherein it comprises several subsets of cellsand switches disposed between these subsets able to dispose two subsetsin series or in parallel.
 2. Photovoltaic energy generation deviceaccording to claim 1, wherein it comprises at least one cell associatedwith at least one cell switch, so as to be able to disconnect it fromthe remainder of the photovoltaic energy generation device. 3.Photovoltaic energy generation device according to claim 2, wherein itcomprises several modules disposed in series comprising at least onecell, and in that each subset of cells comprises one or more moduleslinked in series.
 4. Photovoltaic energy generation device according toclaim 3, wherein each module comprises a lower terminal adapted forconnection with a lower module and an upper terminal adapted forconnection with an upper module, and in that it comprises a modulecomprising at least one branch between its lower terminal and its upperterminal comprising a cell and a cell switch disposed in series. 5.Photovoltaic energy generation device according to claim 1, wherein itcomprises switches for inverting the voltage across the terminals of allor part of the photovoltaic energy generation device and/or modifyingthe assemblage in series or in parallel of subsets of the photovoltaicenergy generation device, which are controlled by at least one controlcircuit disposed at the level of a module or of a subset of thephotovoltaic energy generation device.
 6. Photovoltaic energy generationdevice according to claim 1, wherein it comprises at least oneprocessing circuit at the level of a module or of a subset and/or acentral computer, which drives(drive) cell switches or module switchesor parallel switches and/or switches disposed between subsets to modifythe assemblage in series or in parallel of these subsets and/or switchesto invert the voltage across the terminals of all or part of thephotovoltaic energy generation device, by way of a control circuit. 7.Photovoltaic energy generation device according to claim 1, wherein itcomprises a processing circuit at the level of a module and/or a centralcomputer which implements regulation of a value of voltage and/or outputcurrent of the photovoltaic energy generation device around a setpointvalue by computing the number of subsets to be disposed in series or inparallel and by actuating the switches disposed between these subsets.8. Photovoltaic energy generation device according to claim 1, whereinit comprises several modules disposed in series each comprising severalcells disposed in parallel and/or series, each cell being associatedwith at least one cell switch and each cell comprising a photovoltaiccell, comprising one or more elementary photovoltaic cell(s), and astorage element connected to the terminals of the photovoltaic cell. 9.Photovoltaic energy generation device according to claim 1, wherein itcomprises an arrangement of bricks comprising two parallel branchescomprising respectively a cell and at least one cell switch and at leastone cell switch and a cell, and comprising a transverse branch linkingthe two intermediate terminals of respectively the said two parallelbranches, this transverse branch comprising a cell switch. 10.Photovoltaic energy generation device according to claim 1, wherein itcomprises at least one H-bridge able to invert the voltage across theterminals of all or part of the photovoltaic energy generation device.11. Photovoltaic energy generation device according to claim 1, whereinit comprises at least one module switch connected in parallel with amodule or at least one module, each cell of which is associated with aparallel switch connected in parallel with the said cell and a cellswitch disposed in series, and/or at least one switch disposed inparallel with several modules.
 12. Photovoltaic energy generation deviceaccording to claim 1, wherein it comprises a sensor for measuring thecurrent at the level of a cell, and/or a sensor for measuring thevoltage across the terminals of a cell and/or across the terminals of acell switch, and/or a sensor for measuring the temperature of a celland/or for impedance spectrometry measurement.
 13. Photovoltaic energygeneration device according to claim 1, wherein the cell switch and/ormodule switch and/or parallel switch is a transistor and/or in that thestorage element comprises at least one capacitor.
 14. Photovoltaicenergy generation device according to claim 1, wherein it comprisesthree columns each comprising several modules disposed in series toprovide a three-phase output.
 15. Method for managing a photovoltaicenergy generation device according to claim 1, wherein it comprises astep of computing the number of subsets of the photovoltaic energygeneration device to be disposed in parallel or in series and a step ofdetermining the position of switches disposed between the subsets toattain the computed number.
 16. Method for managing a photovoltaicenergy generation device according to claim 15, wherein it comprises astep of determining the position of several cell switches and/or ofseveral parallel switches of several cells disposed in parallel so as tomaintain cells of the photovoltaic energy generation device in anoperating state in a range around an optimal operating point.
 17. Methodfor managing a photovoltaic energy generation device according to claim15, wherein it comprises; a first computation of the ratio between thedesired output voltage of the photovoltaic energy generation device andthe mean voltage of a subset, thereby giving the number N of subsets tobe placed in series so as to attain, under no load, the desired outputvoltage; computation of a mean deviation between the voltage of thesubsets and their optimal voltage, and feedback so as to approach theoptimal situation, by modifying the output current so as to approach amore favourable situation to attain optimal operation at the level ofeach subset; selection of the N particular subsets to be used, by takingaccount of the deviation between their voltage and their optimalvoltage.
 18. Method for managing a photovoltaic energy generation deviceaccording to claim 15, wherein it comprises a step of regulating thevoltage and/or the output current of the photovoltaic energy generationdevice so as to follow a setpoint value.
 19. Method for managing aphotovoltaic energy generation device according to claim 18, wherein thesetpoint value is variable over time, is for example sinusoidal. 20.Method for managing a photovoltaic energy generation device according toclaim 18, wherein it comprises a step of increasing the number ofsubsets in series if the output voltage of the photovoltaic energygeneration device is less than the setpoint value and a step ofdecreasing the number of subsets in series if the output voltage isgreater than the setpoint value.
 21. Method for managing a photovoltaicenergy generation device according to claim 20, wherein it comprises astep of limiting the frequency of variation of the configuration of thephotovoltaic energy generation device so as to attain regulation withregard to a mean value while preventing the number of subsets in seriesfrom exhibiting too much oscillation.
 22. Method for managing aphotovoltaic energy generation device according to claim 15, wherein itcomprises the following steps: when the voltage across the terminals ofa cell exceeds an optimal voltage corresponding to the optimal operatingpoint, increased by a predefined percentage, at least one cell switch isclosed so as to allow its use to produce a voltage and a current towardsthe output of the device, and/or when the voltage across the terminalsof a cell falls under this optimal voltage decreased by a predefinedpercentage, at least one cell switch is opened, so that it no longerparticipates in the production of voltage and current at the output ofthe device.
 23. Method for managing a photovoltaic energy generationdevice according to claim 15, wherein it comprises a step of charging ofa storage element by a photovoltaic during its disconnection from theremainder of the device.
 24. Method of photovoltaic energy generationdevice management according to claim 15, wherein it implements thefollowing steps: mutual balancing of the modules and/or cells and/orsubsets, using by priority the modules and/or cells and/or subsets whosevoltage is the highest; and/or balancing of the modules and/or cellsand/or subsets by modifying the mean rate of use of the modules and/orcells, and/or subsets but without using the same modules and/or cellsand/or subsets permanently, so that the voltage of the modules and/orcells and/or subsets balances.
 25. Method for managing a photovoltaicenergy generation device according to claim 15, wherein it comprises astep of supplying electrical power to a control circuit for a cellswitch and/or switches disposed between subsets able to dispose twosubsets in series or in parallel and/or for a parallel switch on thebasis of at least one cell of the photovoltaic energy generation device.